RFC 3211 (rfc3211) - Page 3 of 17
Password-based Encryption for CMS
Alternative Format: Original Text Document
RFC 3211 Password-based Encryption for CMS December 2001 The fields of type PasswordRecipientInfo have the following meanings: version is the syntax version number. It MUST be 0. Details of the CMSVersion type are discussed in CMS [RFC 2630], section 10.2.5. keyDerivationAlgorithm identifies the key-derivation algorithm, and any associated parameters, used to derive the KEK from the user-supplied password. If this field is absent, the KEK is supplied from an external source, for example a crypto token such as a smart card. keyEncryptionAlgorithm identifies the key-encryption algorithm, and any associated parameters, used to encrypt the CEK with the KEK. encryptedKey is the result of encrypting the content-encryption key with the KEK. 1.2.2 Rationale Password-based key wrapping is a two-stage process, a first stage in which a user-supplied password is converted into a KEK if required, and a second stage in which the KEK is used to encrypt a CEK. These two stages are identified by the two algorithm identifiers. Although the PKCS #5v2 standard [RFC 2898] goes one step further to wrap these up into a single algorithm identifier, this design is particular to that standard and may not be applicable for other key wrapping mechanisms. For this reason the two steps are specified separately. The current format doesn't provide any means of differentiating between multiple password recipient infos, which would occur for example if two passwords are used to encrypt the same data. Unfortunately there is a lack of existing practice in this area, since typical applications follow the model of encrypting data such as a file with a single password obtained from the user. Without any clear requirements, an appropriate multiple password mechanism would be difficult (perhaps impossible) to define at this time. If sufficient demand emerges then this may be addressed in a future version of this document, for example by adding an optional identification field of an appropriate form. 2 Supported Algorithms This section lists the algorithms that must be implemented. Additional algorithms that should be implemented are also included. Gutmann Standards Track
