Network Working Group P. Hoyer Internet-Draft ActivIdentity Intended status: Standards Track M. Pei Expires: January 10, 2008 VeriSign S. Machani Diversinet A. Vassilev Axalto J. Martinsson PortWise July 9, 2007 Portable Symmetric Key Container draft-hoyer-keyprov-portable-symmetric-key-container-02.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 10, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Hoyer, et al. Expires January 10, 2008 [Page 1] Internet-Draft Portable Symmetric Key Container July 2007 Abstract This document specifies a symmetric key format for transport and provisioning of symmetric keys (One Time Password (OTP) shared secrets or symmetric cryptographic keys) to different types of strong authentication devices. The standard token format enables enterprises to deploy best-of-breed solutions combining components from different vendors into the same infrastructure. This work is a joint effort by the members of OATH (Initiative for Open AuTHentication) to specify a format that can be freely distributed to the technical community. The authors believe that a common and shared specification will facilitate adoption of two- factor authentication on the Internet by enabling interoperability between commercial and open-source implementations. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions used in this document . . . . . . . . . . . . . . 5 3. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1. Offline Use Cases . . . . . . . . . . . . . . . . . . . . 6 3.1.1. Credential migration by end-user . . . . . . . . . . . 6 3.1.2. Bulk import of new credentials . . . . . . . . . . . . 6 3.1.3. Bulk migration of existing credentials . . . . . . . . 6 3.1.4. Credential upload case . . . . . . . . . . . . . . . . 7 3.2. Online Use Cases . . . . . . . . . . . . . . . . . . . . . 7 3.2.1. Online provisioning a credential to end-user's authentication token . . . . . . . . . . . . . . . . . 7 3.2.2. Server to server provisioning of credentials . . . . . 8 3.2.3. Online update of an existing authentication token credential . . . . . . . . . . . . . . . . . . . . . . 8 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Symmetric Key Attributes . . . . . . . . . . . . . . . . . . . 11 5.1. Common Attributes . . . . . . . . . . . . . . . . . . . . 11 5.1.1. Data (OPTIONAL) . . . . . . . . . . . . . . . . . . . 11 5.1.2. KeyAlgorithm (MANDATORY) . . . . . . . . . . . . . . . 11 5.1.3. Usage (MANDATORY) . . . . . . . . . . . . . . . . . . 11 5.1.4. KeyId (MANDATORY) . . . . . . . . . . . . . . . . . . 12 5.1.5. Issuer (MANDATORY) . . . . . . . . . . . . . . . . . . 12 5.1.6. FriendlyName (OPTIONAL) . . . . . . . . . . . . . . . 12 5.1.7. AccessRules (OPTIONAL) . . . . . . . . . . . . . . . . 12 5.1.8. EncryptionMethod (MANDATORY when 'Data' attribute is encrypted)) . . . . . . . . . . . . . . . . . . . . 12 5.1.9. DigestMethod (MANDATORY when Digest is present) . . . 13 5.1.10. OTP and CR specific Attributes (OPTIONAL) . . . . . . 13 6. Key container XML schema definitions . . . . . . . . . . . . . 17 Hoyer, et al. Expires January 10, 2008 [Page 2] Internet-Draft Portable Symmetric Key Container July 2007 6.1. XML Schema Types . . . . . . . . . . . . . . . . . . . . . 17 6.1.1. KeyType . . . . . . . . . . . . . . . . . . . . . . . 18 6.1.2. UsageType . . . . . . . . . . . . . . . . . . . . . . 20 6.1.3. DeviceType . . . . . . . . . . . . . . . . . . . . . . 22 6.1.4. DeviceIdType . . . . . . . . . . . . . . . . . . . . . 22 6.1.5. UserType Type . . . . . . . . . . . . . . . . . . . . 23 6.1.6. KeyContainerType . . . . . . . . . . . . . . . . . . . 24 6.1.7. EncryptionMethodType . . . . . . . . . . . . . . . . . 25 6.1.8. DigestMethodType . . . . . . . . . . . . . . . . . . . 27 6.1.9. AlgorithmIdentifierType . . . . . . . . . . . . . . . 28 6.2. EncryptionAlgorithmType . . . . . . . . . . . . . . . . . 28 6.3. HashAlgorithmType . . . . . . . . . . . . . . . . . . . . 30 6.4. DigestAlgorithmType . . . . . . . . . . . . . . . . . . . 30 6.5. KeyAlgorithmType . . . . . . . . . . . . . . . . . . . . . 31 6.6. valueFormat . . . . . . . . . . . . . . . . . . . . . . . 33 6.7. Data elements . . . . . . . . . . . . . . . . . . . . . . 33 6.7.1. KeyContainer . . . . . . . . . . . . . . . . . . . . . 33 7. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 35 8. Security Considerations . . . . . . . . . . . . . . . . . . . 41 8.1. Payload confidentiality . . . . . . . . . . . . . . . . . 41 8.2. Payload integrity . . . . . . . . . . . . . . . . . . . . 42 8.3. Payload authenticity . . . . . . . . . . . . . . . . . . . 42 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 43 10. Appendix A - Example Symmetric Key Containers . . . . . . . . 44 10.1. Symmetric Key Container with a single Non-Encrypted HOTP Secret Key . . . . . . . . . . . . . . . . . . . . . 44 10.2. Symmetric Key Container with a single Password-based Encrypted HOTP Secret Key . . . . . . . . . . . . . . . . 45 11. Normative References . . . . . . . . . . . . . . . . . . . . . 46 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 48 Intellectual Property and Copyright Statements . . . . . . . . . . 50 Hoyer, et al. Expires January 10, 2008 [Page 3] Internet-Draft Portable Symmetric Key Container July 2007 1. Introduction With increasing use of symmetric key based authentication systems such as systems based one time password (OTP) and challenge response mechanisms, there is a need for vendor interoperability and a standard format for importing, exporting or provisioning symmetric key based credentials from one system to another. Traditionally authentication server vendors and service providers have used proprietary formats for importing, exporting and provisioning these credentials into their systems making it hard to use tokens from vendor A with a server from vendor B. This Internet draft describes a standard format for serializing symmetric key based credentials such as OTP shared secrets for system import, export or network/protocol transport. The goal is that the format will facilitate dynamic provisioning and transfer of a symmetric key such as an OTP shared secret or an encryption key of different types. In the case of OTP shared secrets, the format will facilitate dynamic provisioning using an OTP provisioning protocol to different flavors of embedded tokens for OTP credentials or allow customers to import new or existing tokens in batch or single instances into a compliant system. This draft also specifies the token attributes required for interoperability such as the initial event counter used in the HOTP algorithm [HOTP]. It is also applicable for other time-based or proprietary algorithms. To provide an analogy, in public key environments the PKCS#12 format [PKCS12] is commonly used for importing and exporting private keys and certificates between systems. In the environments outlined in this document where OTP credentials may be transported directly down to smartcards or devices with limited computing capabilities, a format with small (size in bytes) and explicit shared secret configuration attribute information is desirable, avoding complexity of PKCS#12. For example, one would have to use opaque data within PKCS#12 to carry shared secret attributes used for OTP calculations, wherears a more explicit attribute schema definition is better for interoperation and efficiency. Hoyer, et al. Expires January 10, 2008 [Page 4] Internet-Draft Portable Symmetric Key Container July 2007 2. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. In examples, "C:" and "S:" indicate lines sent by the client and server respectively. In the text below, OTP refers to one time password. Hoyer, et al. Expires January 10, 2008 [Page 5] Internet-Draft Portable Symmetric Key Container July 2007 3. Use Cases This section describes a comprehensive list of use cases that inspired the development of this specification. These requirements were used to derive the primary requirement that drove the design. These requirements are covered in the next section. These use cases also help in understanding the applicability of this specification to real world situations. 3.1. Offline Use Cases This section describes the use cases relating to offline transport of credentials from one system to another, using some form of export and import model. 3.1.1. Credential migration by end-user A user wants to migrate a credential from one authentication token (container) to a different authentication token. For example, the authentication tokens may be soft tokens on two different systems (computers or mobile phones). The user can export the credential in a standard format for import into the other authentication token. The key protection mechanism may rely on password-based encryption for soft tokens, a pre-placed hardware-protected transfer key shared between the two systems or may also rely on asymmetric keys/ PKI if available. 3.1.2. Bulk import of new credentials Tokens are manufactured in bulk and associated credentials (key records) need to be loaded into the validation system through a file on portable media. The manufacturer provides the credentials in the form of a file containing records in standard format, typically on a CD. Note that the token manufacturer and the vendor for the validation system may be the same or different. In this case the file usually is protected by a symmetric transport key which was communicated separately outside of the file between the two parties. 3.1.3. Bulk migration of existing credentials An enterprise wants to port credentials from an existing validation system A into a different validation system B. The existing validation system provides the enterprise with a functionality that enables export of credentials (OTP tokens) in a standard format. Hoyer, et al. Expires January 10, 2008 [Page 6] Internet-Draft Portable Symmetric Key Container July 2007 Since the OTP tokens are in the standard format, the enterprise can import the token records into the new validation system B and start using the existing tokens. Note that the vendors for the two validation systems may be the same or different. In this case the file usually is protected by a symmetric transport key which was communicated separately outside of the file between the two validation systems. 3.1.4. Credential upload case User wants to activate and use a new credential against a validation system that is not aware of this credential. This credential may be embedded in the authentication token (e.g. SD card, USB drive) that the user has purchased at the local electronics retailer. Along with the authentication token, the user may get the credential on a CD or a floppy in a standard format. The user can now upload via a secure online channel or import this credential into the new validation system and start using the credential. The key protection mechanism may rely on password-based encryption, or a pre-placed hardware-protected transfer key shared between the token manufacturer and the validation system(s) if available. 3.2. Online Use Cases This section describes the use cases related to provisioning the credentials using some form of a online provisioning protocol. 3.2.1. Online provisioning a credential to end-user's authentication token A mobile device user wants to obtain an OTP credential (shared secret) for use with an OTP soft token on the device. The soft token client from vendor A initiates the provisioning process against a provisioning system from vendor B using a standards-based provisioning protocol such as [DSKPP]. The provisioning system delivers an OTP credential in a standard format that can be processed by the mobile device. The user can download more than one credential in a single session if the provisioning server holds multiple credentials for that user. In a variation of the above, instead of the user's mobile phone, a credential is provisioned in the user's soft token application on a laptop using a network-based online protocol. As before, the provisioning system delivers an OTP credential in a standard format that can be processed by the soft token on the PC. Hoyer, et al. Expires January 10, 2008 [Page 7] Internet-Draft Portable Symmetric Key Container July 2007 3.2.2. Server to server provisioning of credentials Sometimes, instead of importing token information from manufacturer using a file, an OTP validation server may download the credential seed records using an online protocol. The credentials can be downloaded in a standard format that can be processed by a validation system. In another scenario, an OTA (over-the-air) credential provisioning gateway that provisions credentials to mobile phones may obtain credentials from the credential issuer using an online protocol. The credentials are delivered in a standard format that can be processed by the OTA credential provisioning gateway and subsequently sent to the end-user's mobile phone. 3.2.3. Online update of an existing authentication token credential The end-user or the credential issuer wants to update or configure an existing credential in the authentication token and requests a replacement credential container. The container may or may not include a new secret key and may include new or updated secret key attributes such as a new counter value in HOTP credential case, a new logo, a modified response format or length, a new friendly name, etc. Hoyer, et al. Expires January 10, 2008 [Page 8] Internet-Draft Portable Symmetric Key Container July 2007 4. Requirements This section outlines the most relevant requirements that are the basis of this work. Several of the requirements were derived from use cases described above. R1: The format MUST support transport of multiple types of symmetric key credentials including HOTP, other OTP, challenge- response, etc. R2: The format MUST handle the symmetric key itself as well of attributes that are typically associated with symmetric keys. Some of these attributes may be * Unique Key Identifier * Issuer information * Algorithm ID * Algorithm mode * Issuer Name * Issuer logo * Credential friendly name * Event counter value (moving factor for OTP algorithms) * Time value R3: The format SHOULD support both offline and online scenarios. That is it should be serializable to a file as well as it should be possible to use this format in online provisioning protocols R4: The format SHOULD allow bulk representation of symmetric key credentials. R5: The format SHOULD be portable to various platforms. Furthermore, it SHOULD be computationally efficient to process. R6: The format MUST provide appropriate level of security in terms of data encryption and data integrity. Hoyer, et al. Expires January 10, 2008 [Page 9] Internet-Draft Portable Symmetric Key Container July 2007 R7: For online scenarios the format SHOULD NOT rely on transport level security (e.g., SSL/TLS) for core security requirements. R8: The format SHOULD be extensible. It SHOULD enable extension points allowing vendors to specify additional attributes in the future. R9: The format SHOULD allow for distribution of key derivation data without the actual symmetric key itself. This is to support symmetric key management schemes that rely on key derivation algorithms based on a pre-placed master key. The key derivation data typically consists of a reference to the key, rather than the key value itself. R10: The format SHOULD allow for additional lifecycle management operations such as counter resynchronization. Such processes require confidentiality between client and server, thus could use a common secure container format, without the transfer of key material. R11: The format MUST support the use of pre-shared symmetric keys to ensure confidentiality of sensitive data elements. R12: The format MUST support a password-based encryption (PBE) [PKCS5] scheme to ensure security of sensitive data elements. This is a widely used method for various provisioning scenarios. R13: The format SHOULD support asymmetric encryption algorithms such as RSA to ensure end-to-end security of sensitive data elements. This is to support scenarios where a pre-set shared encryption key is difficult to use. Hoyer, et al. Expires January 10, 2008 [Page 10] Internet-Draft Portable Symmetric Key Container July 2007 5. Symmetric Key Attributes The symmetric key includes a number of data attributes that define the type of the key its usage and associated meta-information required during the provisioning, configuration, access or usage in the host device. 5.1. Common Attributes 5.1.1. Data (OPTIONAL) Defines the data attributes of the symmetric key. Each is a name value pair which has both a base64 encoded value and a base 64 encoded valueDigest. The value can be encrypted. If the container has been encrypted the valueDigest MUST be populated with the digest of the unencrypted value. This is also where the key value is held, therefore the follwoing list of attribute names have been reserved: SECRET: the shared secret key value in binary, base64 encoded COUNTER: the event counter for event based OTP algorithms. 8 bytes unsigned integer in big endian (i.e. network byte order) form base64 encoded TIME: the time for time based OTP algorithms. 8 bytes unsigned integer in big endian (i.e. network byte order) form base64 encoded (Number of seconds since 1970) TIME_INTERVAL: the time interval value for time based OTP algorithms. 8 bytes unsigned integer in big endian (i.e. network byte order) form base64 encoded. 5.1.2. KeyAlgorithm (MANDATORY) Defines the type of algorithm of the secret key and MUST be set to one of the values defined in Section 6.5. If 'OTHER' is specified an extension value MUST be set in the 'ext-KeyAlgorithm' attribute. 5.1.3. Usage (MANDATORY) Defines the intended usage of the key and is a combination of one or more of the following (set to true): Hoyer, et al. Expires January 10, 2008 [Page 11] Internet-Draft Portable Symmetric Key Container July 2007 OTP: the key will be used for OTP generation CR: the key will be used for Challenge/Response purposes ENCRYPT: the key will be used for data encryption purposes SIGN: the key will be used to generate a signature or keyed hashing for data integrity or authentication purposes. UNLOCK: the key will be used for an inverse challenge response in the case a user has locked the device by entering a wrong PIN too many times (for devices with PIN-input capability) Additional attributes that are specific to the usage type MAY be required. Section 6.1 describes OTP and CR specific attributes. 5.1.4. KeyId (MANDATORY) A unique and global identifier of the symmetric key. The identifier is defined as a string of alphanumeric characters. 5.1.5. Issuer (MANDATORY) The key issuer name, this is normally the name of the organisation that issues the key to the end user of the key. For example MyBank issuing hardware tokens to their retail banking users 'MyBank' would be the issuer. The Issuer is defined as a String. 5.1.6. FriendlyName (OPTIONAL) The user friendly name that is assigned to the secret key for easy reference. The FriendlyName is defined as a String. 5.1.7. AccessRules (OPTIONAL) Defines a set of access rules and policies for the protection of the key on the host Device. Currently only the userPIN policy is defined. The userPIN policy specifies whether the user MUST enter a PIN (for devices with PIN input capability) in order to unlock or authenticate to the device hosting the key container. The userPIN is defined as a Boolean (TRUE or FALSE). When the user PIN is required, the policy MUST be set to TRUE. If the userPIN is NOT provided, implementations SHALL default the value to FALSE. 5.1.8. EncryptionMethod (MANDATORY when 'Data' attribute is encrypted)) Identifies the encryption algorithm and possible parameters used to protect the Secret Key data in the container and MUST be set to one Hoyer, et al. Expires January 10, 2008 [Page 12] Internet-Draft Portable Symmetric Key Container July 2007 of the values defined in Section 6.2. If 'OTHER' is specified an extension value MUST be set in the 'ext-algorithm' attribute. When the value is set to NONE, implementations SHALL ensure the privacy of the key data through other standard mechanisms e.g. transport level encryption. When the KeyContainer contains more than one key and EncryptionMethod is different from NONE, the same encryption key MUST be used to encrypt all the key data elements in the container. 5.1.9. DigestMethod (MANDATORY when Digest is present) Identifies the algorithm and possible parameters used to generate a digest of the the Secret Key data. The digest guarantees the integrity and the authenticity of the key data. The Digest algorithm MUST be set to one of the values defined in Section 6.4. If 'OTHER' is specified an extension value MUST be set in the 'ext-algorithm' attribute. See Section 6.1.8 for more information on Digest data value type. 5.1.10. OTP and CR specific Attributes (OPTIONAL) When the key usage is set to OTP or CR, additional attributes MUST be provided to support the OTP and/or the response computation as required by the underlying algorithm and to customize or configure the outcome of the computation (format, length and usage modes). 5.1.10.1. ChallengeFormat (MANDATORY) The ChallengeFormat attribute defines the characteristics of the challenge in a CR usage scenario. The Challenge attribute is defined by the following sub-attributes: 1. Format (MANDATORY) Defines the format of the challenge accepted by the device and MUST be one of the values defined in Section 6.6 2. CheckDigit (OPTIONAL) Defines if the device needs to check the appended Luhn check digit contained in a provided challenge. This is only valid if the Format attribute is'DECIMAL'. Value MUST be: Hoyer, et al. Expires January 10, 2008 [Page 13] Internet-Draft Portable Symmetric Key Container July 2007 TRUE device will check the appended Luhn check digit in a provided challenge FALSE device will not check appended Luhn check digit in challenge 3. Min (MANDATORY) Defines the minimum size of the challenge accepted by the device for CR mode. If the Format attribute is 'DECIMAL','HEXADECIMAL' or 'ALPHANUMERIC' this value indicates the minimum number of digits/characters. If the Format attribute is 'BASE64' or 'BINARY', this value indicates the minimum number of bytes of the unencoded value. Value MUST be: Unsigned integer. 4. Max (MANDATORY) Defines the maximum size of the challenge accepted by the device for CR mode. If the Format attribute is 'DECIMAL','HEXADECIMAL' or 'ALPHANUMERIC' this value indicates the maximum number of digits/characters. If the Format attribute is 'BASE64' or 'BINARY', this value indicates the maximum number of bytes of the unencoded value. Value MUST be: Unsigned integer. 5.1.10.2. ResponseFormat (MANDATORY) The ResponseFormat attribute defines the characteristics of the result of a computation. This defines the format of the OTP or of the response to a challenge. The Response attribute is defined by the following sub-attributes: Hoyer, et al. Expires January 10, 2008 [Page 14] Internet-Draft Portable Symmetric Key Container July 2007 1. Format (MANDATORY) Defines the format of the response generated by the device and MUST be one of the values defined in Section 6.6 2. CheckDigit (OPTIONAL) Defines if the device needs to append a Luhn check digit to the response. This is only valid if the Format attribute is'DECIMAL'. Value MUST be: TRUE device will append a Luhn check digit to the response. FALSE device will not append a Luhn check digit to the response. 3. Length (MANDATORY) Defines the length of the response generated by the device. If the Format attribute is 'DECIMAL','HEXADECIMAL' or 'ALPHANUMERIC' this value indicates the number of digits/ characters. If the Format attribute is 'BASE64' or 'BINARY', this value indicates the number of bytes of the unencoded value. Value MUST be: Unsigned integer. 5.1.10.3. AppProfileId (OPTIONAL) Defines the application profile id related to attributes present on a smart card that have influence when computing a response. An example could be an EMV MasterCard CAP [CAP] application on a card that contains attributes or uses fixed data for a specific batch of cards such as: IAF Internet authentication flag CVN Cryptogram version number, for example (MCHIP2, MCHIP4, VISA 13, VISA14) Hoyer, et al. Expires January 10, 2008 [Page 15] Internet-Draft Portable Symmetric Key Container July 2007 AIP (Application Interchange Profile), 2 bytes TVR Terminal Verification Result, 5 bytes CVR The card verification result AmountOther TransactionDate TerminalCountryCode TransactionCurrencyCode AmountAuthorised IIPB These values are not contained within attributes in the container but are shared between the manufacturing and the validation service through this unique AppProfileId. Hoyer, et al. Expires January 10, 2008 [Page 16] Internet-Draft Portable Symmetric Key Container July 2007 6. Key container XML schema definitions The portable key container is defined by the following entities: 1. KeyContainer entity 2. Device entity 3. Key entity 4. User entity A KeyContainer MAY contain one or more Device entities. A Device MAY contain one or more Key entities and may be associated to one or more User entities. The figure below indicates a possible relationship diagram of a container. -------------------------------------------- | KeyContainer | | | | ----------------- ----------------- | | | Device 1 | | Device n | | | | | | | | | | ----------- | | ----------- | | | | | Key 1 | | | | Key n | | | | | ----------- | | ----------- | | | | | | | | | | | | | | | | | | | | | | ----------- | | ----------- | | | | | Key m | | | | Key p | | | | | ----------- | | ----------- | | | ----------------- ----------------- | | | | | | | | | | | | --------- --------- --------- | | | User 1 | | User 1 | | User n | | | --------- --------- --------- | | | -------------------------------------------- 6.1. XML Schema Types The following types are defined to represent the portable key container entities and associated attributes. Hoyer, et al. Expires January 10, 2008 [Page 17] Internet-Draft Portable Symmetric Key Container July 2007 6.1.1. KeyType The KeyType represents the key entity in the KeyContainer. The KeyType is defined as follows: The components of the KeyType have the following meanings (see Section 5 for further information): o of type UsageType defines the usage of the Secret Key. The Usage attribute is described in Section 5.1.3. o identifies the issuer of the Secret Key. The Issuer attribute is described in Section 5.1.5. o is a user friendly name that is assigned to the Secret Key for easy reference. o conveys the data attributes (eg the Secret Key) in name (string) value (base64 encoded) pairs. The value can be encrypted, in this case a digest of the non-encrypted data is present. The component is further described below. Hoyer, et al. Expires January 10, 2008 [Page 18] Internet-Draft Portable Symmetric Key Container July 2007 o Defines the rules for accessing the credential on the device e.g. a password must be provided by the user to view credential info or use the credential to generate an OTP response o KeyId is a global identifier of the Secret Key. See Section 5.1.4. o KeyAlgorithm defines the algorithm used with the Secret Key. The type values are defined in Section 6.5. If 'OTHER' is specified an extension value MUST be set in the 'ext-KeyAlgorithm' attribute. o ext-KeyAlgorithm is the extension point for KeyAlgorithms not already defined Section 6.5 o Logo of type LogoType associates display logos with this Secret Key o Expiry defines the expiry date of the Secret Key in format DD/MM/ YYYY The element is of type and is defined as follows: The 'Name' attribute defines the name of the name-value pair, the follwoing list of attribute names have been reserved: SECRET: the key key value in binary, base64 encoded COUNTER: the event counter for event based OTP algorithms. 8 bytes unsigned integer in big endian (i.e. network byte order) form base64 encoded TIME: the time for time based OTP algorithms. 8 bytes unsigned integer in big endian (i.e. network byte order) form base64 encoded (Number of seconds since 1970) TIME_INTERVAL: the time interval value for time based OTP algorithms. 8 bytes unsigned integer in big endian (i.e. network byte order) form base64 encoded. Hoyer, et al. Expires January 10, 2008 [Page 19] Internet-Draft Portable Symmetric Key Container July 2007 The element in the DataType conveys the value of the name- value pair in base 64 encoding. The value MAY be encrypted or in clear text as per the EncryptionMethod data element in the KeyContainer (see Section 6.1.6 for details about KeyContainerType). When the value is encrypted, the digest value in 'ValueDigest' MUST be provided. The digest MUST be calculated on the unencrypted value and MUST use one of the Digest algorithms specified in DigestMethodType element of the KeyContainer. The MAC key for the MAC calculation should use the same key as the encryption key specified in the EncryptionMethod unless a separate MAC key is specified. When PBE method is used for encryption, a different password is recommended for the MAC key derivation. When the key data is in clear text, the KeyContainer payload signature MAY be used to check the integrity of the key octets. 6.1.2. UsageType The UsageType defines the usage attribute of the key entity. The UsageType is defined as follows: Hoyer, et al. Expires January 10, 2008 [Page 20] Internet-Draft Portable Symmetric Key Container July 2007 The UsageType components have the following meanings: o the AlgorithmIdentifier as defined in [OCRA]]. o hold the challenge attributes in CR based algorithm computations. o holds the algorithm response attributes. Hoyer, et al. Expires January 10, 2008 [Page 21] Internet-Draft Portable Symmetric Key Container July 2007 o holds a set of access rules and policies for the key once provisioned on the Device. Currently only the userPIN attribute is defined. The userPIN indicates whether the user MUST provide a PIN to unlock the key. o Is the unique shared identifier for out of band shared common parameters. 6.1.3. DeviceType The DeviceType type represents the Device entity in the Container. A Device MAY be bound to a user and MAY contain more than one keys. It is recommended that a key is bound to one and only one Device. The DeviceType is defined as follows: The components of the DeviceType have the following meanings: o , a unique identifier for the device, defined by the DeviceId type. o , represents the key entity defined by the KeyType. o , optionally identifies the owner or the user of the Device, as defined by the UserType . 6.1.4. DeviceIdType The DeviceId type represents the identifying criteria to uniquely identify the device that contains the associated keys. Since devices can come in different form factors such as hardware tokens, smartcards, soft tokens in a mobile phone or PC etc this type allows different criteria to be used. Combined though the criteria MUST uniquely identify the device. For example for hardware tokens the combination of SerialNo and Manufacturer will uniquely identify a device but not serialNo alone since two different token manufacturers might issue devices with the same serialnumber (similar to the Hoyer, et al. Expires January 10, 2008 [Page 22] Internet-Draft Portable Symmetric Key Container July 2007 IssuerDN and serialnumber of a certificate). For keys hold on banking cards the identification of the device is often done via the Primary Account Number (PAN, the big number printed on the front of the card) and an expiry date of the card. DeviceId is an extensible type that allows all these different ways to uniquely identify a specific key containing device. The DeviceIdType is defined as follows: The components of the DeviceId type have the following meanings: o , the manufacturer of the device. o , the model of the device (e.g one-button-HOTP-token-V1) o , the serial number of the device or the PAN (primary account number) in case of EMV (Europay-MasterCard-Visa) smart cards. o , the issue number in case of smart cards with the same PAN, equivalent to a PSN (PAN Sequence Number). o , the expiry date of a device (such as the one on an EMV card,used when issue numbers are not printed on cards). In format DD/MM/YYYY 6.1.5. UserType Type The UserType represents the identifying criteria to uniquely identify the user who is bound to this device. The UserType is defined as follows: Hoyer, et al. Expires January 10, 2008 [Page 23] Internet-Draft Portable Symmetric Key Container July 2007 The components of the UserType type have the following meanings: o , user first name. o , user last name. o , user id (UID) or user name. o , user organization name. 6.1.6. KeyContainerType The KeyContainerType represents the key container entity. A Container MAY contain more than one Device entity; each Device entity MAY contain more than one Key entity. The KeyContainerType is defined as follows: Hoyer, et al. Expires January 10, 2008 [Page 24] Internet-Draft Portable Symmetric Key Container July 2007 The components of the KeyContainer have the following meanings: o version, the version number for the portable key container format (the XML schema defined in this document). o , the encryption method used to protect the Key data attributes o , the digest method used to sign the unencrypted the Secret Key data attributes o , the host Device for one or more Keys. o , contains the signature value of the Container. When the signature is applied to the entire container, it MUST use XML Signature methods as defined in [XMLSIG]. The signature is enveloped. 6.1.7. EncryptionMethodType The EncryptionMethodType defines the algorithm and parameters used to encrypt the Secret Key data attributes in the Container. The encryption is applied on each individual Secret Key data in the Hoyer, et al. Expires January 10, 2008 [Page 25] Internet-Draft Portable Symmetric Key Container July 2007 Container. The encryption method MUST be the same for all Secret Key data in the container. The EncryptionMethodType is defined as follows: The components of the EncryptionMethodType have the following meanings: o algorithm: identifies the encryption algorithm used to protect the Secret Key data. When 'NONE' is specified, implementations MUST guarantee the privacy of the Secret Key Data through other mechanisms e.g. through transport level security. If 'OTHER' is specified an extension value MUST be set in the 'ext-algorithm' attribute. Please see EncryptionAlgorithmType for more information on supported algorithms o : conveys the Salt when [PKCS5] password-based encryption is applied. o : conveys the iteration count value in [PKCS5] password-based encryption if it is different from the default value. o : conveys the initialization vector for CBC based encryption algorithms. It is recommended for security reasons to transmit Hoyer, et al. Expires January 10, 2008 [Page 26] Internet-Draft Portable Symmetric Key Container July 2007 this value out of band and treat it the same manner as the key value. o : identifies a unique label for a pre-shared encryption key. o : conveys the information of the key if an RSA algorithm has been used. o : conveys the OAEP parameters if an RSA algorithm has been used. o : conveys the digest algorithm if an RSA algorithm has been used. 6.1.8. DigestMethodType The DigestMethodType defines the algorithm and parameters used to create the digest on the unencrypted Secret Key data in the Container. The digest is applied on each individual Secret Key data in the Container before encryption. The digest method MUST be the same for all Secret Key data in the container. Unless a different digest key is specified it is assumed that keyed digest algorithms will use the same key as for encryption The DigestMethodType is defined as follows: The components of the DigestMethodType have the following meanings: o algorithm, identifies the digest algorithm used to protect the Secret Key data. Please see DigestAlgorithmType for more information on supported algorithms o : identifies a unique label for a pre-shared digest key. Hoyer, et al. Expires January 10, 2008 [Page 27] Internet-Draft Portable Symmetric Key Container July 2007 6.1.9. AlgorithmIdentifierType The AlgorithmIdentiferType defines the Algorithm identifier (AI) specified in [OCRA]. The AlgorithmIdentifierType is defines as follows: See [OCRA] for a full description of the components of the AlgorithmIdentifierType. 6.2. EncryptionAlgorithmType The EncryptionAlgorithmType defines the allowed algorithms for encrypting the Secret Key data in the Container. The EncryptionAlgorithmType is defined as follows: Hoyer, et al. Expires January 10, 2008 [Page 28] Internet-Draft Portable Symmetric Key Container July 2007 NONE when no encryption is applied on the key PBE-3DES112-CBC when password-based encryption is applied using a 112-bit 3DES key in CBC mode PBE-3DES168-CBC when password-based encryption is applied using a 168-bit 3DES key in CBC mode PBE-AES128-CBC when password-based encryption is applied using a 128-bit AES key in CBC mode PBE-AES192-CBC when password-based encryption is applied using a 192-bit AES key in CBC mode is applied. PBE-AES256-CBC password-based encryption is applied using a 256- bit AES key in CBC mode is applied. 3DES112-CBC encryption using a pre-shared 112-bit 3DES key in CBC mode is applied. 3DES168-CBC encryption using a pre-shared 168-bit 3DES key in CBC mode is applied. AES128-CBC encryption using a pre-shared 128-bit AES key in CBC mode is applied. Hoyer, et al. Expires January 10, 2008 [Page 29] Internet-Draft Portable Symmetric Key Container July 2007 AES192-CBC encryption using a pre-shared 192-bit AES key in CBC mode is applied. AES256-CBC encryption using a pre-shared 256-bit AES key in CBC mode is applied. RSA-1_5 The RSAES-PKCS1-v1_5 algorithm, specified in [PKCS1], takes no explicit parameters. RSA-OAEP-MGF1P The same algorithm as defined in section 5.4.2 RSA- OAEP in [XMLENC] It is the RSAES-OAEP-ENCRYPT algorithm, as specified in [PKCS1], it takes three parameters. The two user specified parameters are a MANDATORY message digest function and an OPTIONAL encoding octet string OAEPparams. The message digest function is indicated by the Algorithm attribute of a child ds: DigestMethod element and the mask generation function, the third parameter, is always MGF1 with SHA1 (mgf1SHA1Identifier). OTHER extension point for not already defined algorithms in this list. 6.3. HashAlgorithmType The HashAlgorithmType defines the allowed algorithms for generating a digest in the RSA algorithms. The HashAlgorithmType is defined as follows: SHA1 when the digest was performed using the SHA1 algorithm SHA192 when the digest was performed using the SHA192 algorithm SHA256 when the digest was performed using the SHA256 algorithm 6.4. DigestAlgorithmType The DigestAlgorithmType defines the allowed algorithms for generating a digest on the unencrypted Secret Key data in the Container. Hoyer, et al. Expires January 10, 2008 [Page 30] Internet-Draft Portable Symmetric Key Container July 2007 The DigestAlgorithmType is defined as follows: HMAC-SHA1 when the digest was performed using the HMAC-SHA1 algorithm HMAC-SHA192 when the digest was performed using the HMAC-SHA192 algorithm HMAC-SHA256 when the digest was performed using the HMAC-SHA256 algorithm OTHER extension point for not already defined algorithms in this list. 6.5. KeyAlgorithmType The KeyAlgorithmType defines the algorithms in which the Secret Key data is used. The KeyAlgorithmType is defined as follows: Hoyer, et al. Expires January 10, 2008 [Page 31] Internet-Draft Portable Symmetric Key Container July 2007 3DES112, a 112-bit 3DES key (a.k.a. two-key 3DES) 3DES168, a 168-bit parity-checked 3DES key ACTI, algorithm family from ActivIdentity AES128, a 128-bit AES key AES192, a 192-bit AES key AES256, a 256-bit AES key ANSIX9.9, ANSI X9.9 algorithm DES, a standard DES key HOTP, as defined in [HOTP] MKEYLABEL, master key abel or name when an embedded device key is used to derive the Key RSASECUREID, SecureId algorithm family from RSA VASCO, algorithm family from Vasco OTHER extension point for not already defined algorithms in this list. Hoyer, et al. Expires January 10, 2008 [Page 32] Internet-Draft Portable Symmetric Key Container July 2007 6.6. valueFormat The valueFormat defines allowed formats for challenges or responses in the OTP algorithms. The valueFormat is defined as follows: DECIMAL Only numerical digits HEXADECIMAL Hexadecimal response ALPHANUMERIC All letters and numbers (case sensitive) BASE64 Base 64 encoded BINARY Binary data, this is mainly used in case of connected devices 6.7. Data elements 6.7.1. KeyContainer The KeyContainer data element is defined as: The KeyContainer data element is of type KeyContainerType defined in Section 6.1.6. The EncryptionMethod data element in the KeyContainer defines the encryption algorithm used to protect the Key data. In a multi-key KeyContainer, the same encryption method and the same encryption key MUST be used for all key data elements. The KeyContainer data element MAY contain multiple Device data elements, allowing for bulk provisioning of keys. Hoyer, et al. Expires January 10, 2008 [Page 33] Internet-Draft Portable Symmetric Key Container July 2007 The Signature data element is of type as defined in [XMLSIG] and MAY be omitted in the KeyContainer data element when application layer provisioning or transport layer provisioning protocols provide the integrity and authenticity of the payload between the sender and the recipient of the container. When required, this specification recommends using a symmetric key based signature with the same key used in the encryption of the secret key data. The signature is enveloped. Hoyer, et al. Expires January 10, 2008 [Page 34] Internet-Draft Portable Symmetric Key Container July 2007 7. Formal Syntax The following syntax specification uses the widely adopted XML schema format as defined by a W3C recommendation (http://www.w3.org/TR/xmlschema-0/). It is a complete syntax definition in the XML Schema Definition format (XSD) All implentations of this standard must comply with the schema below. Hoyer, et al. Expires January 10, 2008 [Page 35] Internet-Draft Portable Symmetric Key Container July 2007 Hoyer, et al. Expires January 10, 2008 [Page 37] Internet-Draft Portable Symmetric Key Container July 2007 Hoyer, et al. Expires January 10, 2008 [Page 38] Internet-Draft Portable Symmetric Key Container July 2007 Hoyer, et al. Expires January 10, 2008 [Page 39] Internet-Draft Portable Symmetric Key Container July 2007 Hoyer, et al. Expires January 10, 2008 [Page 40] Internet-Draft Portable Symmetric Key Container July 2007 8. Security Considerations The portable key container carries sensitive information (e.g., cryptographic keys) and may be transported across the boundaries of one secure perimeter to another. For example, a container residing within the secure perimeter of a back-end provisioning server in a secure room may be transported across the internet to an end-user device attached to a personal computer. This means that special care must be taken to ensure the confidentiality, integrity, and authenticity of the information contained within. 8.1. Payload confidentiality By design, the container allows two main approaches to guaranteeing the confidentiality of the information it contains while transported. First, the container key data payload may be encrypted. In this case no transport layer security is required. However, standard security best practices apply when selecting the strength of the cryptographic algorithm for payload encryption. Symmetric cryptographic cipher should be used - the longer the cryptographic key, the stronger the protection. At the time of this writing both 3DES and AES are recommended algorithms but 3DES may be dropped in the relatively near future. Applications concerned with algorithm longevity are advised to use AES. In cases where the exchange of encryption keys between the sender and the receiver is not possible, asymmetric encryption of the secret key payload may be employed. Similarly to symmetric key cryptography, the stronger the asymmetric key, the more secure the protection is. If the payload is encrypted with a method that uses one of the password-based encryption methods provided above, the payload may be subjected to password dictionary attacks to break the encryption password and recover the information. Standard security best practices for selection of strong encryption passwords apply [Schneier]. Practical implementations should use PBESalt and PBEIterationCount when PBE encryption is used. Different PBESalt value per credential record should be used for best protection. The second approach to protecting the confidentiality of the payload is based on using transport layer security. The secure channel established between the source secure perimeter (the provisioning server from the example above) and the target perimeter (the device attached to the end-user computer) utilizes encryption to transport the messages that travel across. No payload encryption is required Hoyer, et al. Expires January 10, 2008 [Page 41] Internet-Draft Portable Symmetric Key Container July 2007 in this mode. Secure channels that encrypt and digest each message provide an extra measure of security, especially when the signature of the payload does not encompass the entire payload. Because of the fact that the plain text payload is protected only by the transport layer security, practical implementation must ensure protection against man-in-the-middle attacks [Schneier]. Validating the secure channel end-points is critically important for eliminating intruders that may compromise the confidentiality of the payload. 8.2. Payload integrity The portable symmetric key container provides a mean to guarantee the integrity of the information it contains through digital signatures. For best security practices, the digital signature of the container should encompass the entire payload. This provides assurances for the integrity of all attributes. It also allows verification of the integrity of a given payload even after the container is delivered through the communication channel to the target perimeter and channel message integrity check is no longer possible. 8.3. Payload authenticity The digital signature of the payload is the primary way of showing its authenticity. The recipient of the container may use the public key associated with the signature to assert the authenticity of the sender by tracing it back to a preloaded public key or certificate. Note that the digital signature of the payload can be checked even after the container has been delivered through the secure channel of communication. A weaker payload authenticity guarantee may be provided by the transport layer if it is configured to digest each message it transports. However, no authenticity verification is possible once the container is delivered at the recipient end. This approach may be useful in cases where the digital signature of the container does not encompass the entire payload. Hoyer, et al. Expires January 10, 2008 [Page 42] Internet-Draft Portable Symmetric Key Container July 2007 9. Acknowledgements The authors of this draft would like to thank the following people for their contributions and support to make this a better specification: Shuh Chang, Siddhart Bajaj, Stu Veath, Kevin Lewis, and Andrea Doherty. Hoyer, et al. Expires January 10, 2008 [Page 43] Internet-Draft Portable Symmetric Key Container July 2007 10. Appendix A - Example Symmetric Key Containers All examples are syntactically correct and compatible with the XML schema in section 7. However, , Key and Key data values are fictitious 10.1. Symmetric Key Container with a single Non-Encrypted HOTP Secret Key Token Manufacturer 98765432187 01/01/2008 Credential Issuer MyFirstToken WldjTHZwRm9YTkhBRytseDMrUnc= WldjTHZwRm9YTkhBRytseDM= WldjTHZwRm9YTkhBRytseDMrUnc= WldjTHZwRm9YTkhBRytseDM= Hoyer, et al. Expires January 10, 2008 [Page 44] Internet-Draft Portable Symmetric Key Container July 2007 10.2. Symmetric Key Container with a single Password-based Encrypted HOTP Secret Key y6TzckeLRQw= 999 Token Manufacturer 98765432187 01/01/2008 Credential Issuer MySecondToken 7JHUyp3azOkqJENSsh6b2vxXzwGBYypzJxEr+ikQAa229KV/BgZhGA== WldjTHZwRm9YTkhBRytseDMrUnc= 7JHUyp3azOkqJENSsh6b2vxXzwGBYypzJxEr+ikQAa229KV/BgZhGA== WldjTHZwRm9YTkhBRytseDMrUnc= Hoyer, et al. Expires January 10, 2008 [Page 45] Internet-Draft Portable Symmetric Key Container July 2007 11. Normative References [CAP] MasterCard International, "Chip Authentication Program Functional Architecture", September 2004. [DSKPP] "Dynamic Symmetric Key Provisioning Protocol", Internet Draft Informational, URL: http://tools.ietf.org/wg/ keyprov/draft-doherty-keyprov-dskpp-00.txt, June 2007. [HOTP] MRaihi, D., "HOTP: An HMAC-Based One Time Password Algorithm", RFC 4226, URL: http://rfc.sunsite.dk/rfc/rfc4226.html, December 2005. [OATH] "Initiative for Open AuTHentication", URL: http://www.openauthentication.org. [OATHRefArch] OATH, "Reference Architecture", URL: http://www.openauthentication.org, Version 1.0, 2005. [OCRA] MRaihi, D., "OCRA: OATH Challenge Response Algorithm", Internet Draft Informational, URL: http://www.ietf.org/ internet-drafts/ draft-mraihi-mutual-oath-hotp-variants-01.txt, December 2005. [PKCS1] Kaliski, B., "RFC 2437: PKCS #1: RSA Cryptography Specifications Version 2.0.", URL: http://www.ietf.org/rfc/rfc2437.txt, Version: 2.0, October 1998. [PKCS12] RSA Laboratories, "PKCS #12: Personal Information Exchange Syntax Standard", Version 1.0, URL: ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-12/. [PKCS5] RSA Laboratories, "PKCS #5: Password-Based Cryptography Standard", Version 2.0, URL: ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-5/, March 1999. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [Schneier] Schneier, B., "Secrets and Lies: Digitial Security in a Networked World", Wiley Computer Publishing, ISBN 0-8493- 8253-7, 2000. Hoyer, et al. Expires January 10, 2008 [Page 46] Internet-Draft Portable Symmetric Key Container July 2007 [XMLENC] Eastlake, D., "XML Encryption Syntax and Processing.", URL: http://www.w3.org/TR/xmlenc-core/, December 2002. [XMLSIG] Eastlake, D., "XML-Signature Syntax and Processing", URL: http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/, W3C Recommendation, February 2002. Hoyer, et al. Expires January 10, 2008 [Page 47] Internet-Draft Portable Symmetric Key Container July 2007 Authors' Addresses Philip Hoyer ActivIdenity, Inc. 109 Borough High Street London, SE1 1NL UK Phone: +44 (0) 20 7744 6455 Email: Philip.Hoyer@actividentity.com Mingliang Pei VeriSign, Inc. 487 E. Middlefield Road Mountain View, CA 94043 USA Phone: +1 650 426 5173 Email: mpei@verisign.com Salah Machani Diversinet, Inc. 2225 Sheppard Avenue East Suite 1801 Toronto, Ontario M2J 5C2 Canada Phone: +1 416 756 2324 Ext. 321 Email: smachani@diversinet.com Apostol T. Vassilev Axalto Inc. 8311 N. FM 620 Austin, TX 78726 USA Phone: +1 512 331 3723 Email: vassilev@axalto.com Hoyer, et al. Expires January 10, 2008 [Page 48] Internet-Draft Portable Symmetric Key Container July 2007 Jon Martinsson PortWise AB F?gatan 33 / Kista Science Tower Kista, SE 164 21 Sweden Phone: +46 8 562 914 55 Email: jon.martinsson@portwise.com Hoyer, et al. Expires January 10, 2008 [Page 49] Internet-Draft Portable Symmetric Key Container July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Hoyer, et al. Expires January 10, 2008 [Page 50]