Denis Pinkas. Bull SA. Denis.Pinkas@bull.net Cryptographic Maintenance Policy IETF LTANS meeting in Paris August, 1rst , 2005 Denis Pinkas. Bull SA. Denis.Pinkas@bull.net

The Cryptographic Maintenance Policy applies both to encryption and to electronic signatures For encryption: the LTAS shall check that the encryption algorithms algorithms are still beyond attack during their whole archiving period, and, if not, shall warn the submitter and or the retrievers. For electronic signatures: make sure that they can be tested during their whole archiving period, and if not, apply a maintenance process.

The focus is now only on Cryptographic Maintenance Policies applicable to electronic signatures

A few definitions and concepts (1/3) Cryptographic maintenance policy for digitally signed objects: a named set of rules that defines how to maintain the validity of digitally signed objects should one of the hash functions or asymmetrical algorithm used to create a digital signature of a signed object become weak or one of the private keys used to create a digital signature of a signed object be compromised or become weak. A cryptographic maintenance policy: MUST be unambiguously identified by an object identifier (e.g. an OID), MUST include a validity period, MUST specify the Time-Stamping Units (TSU) recognized under that policy, MAY unambiguously reference a sequence of one or more previously defined cryptographic maintenance policies.

A few definitions and concepts (2/3) Critical cryptographic parameters: a collection of cryptographic parameters, together with their associated parameters, if any (e.g. key lengths), to be used to maintain the validity of digitally signed objects under a cryptographic maintenance policy. Critical cryptographic parameters shall include : data objects describing all the algorithms, and the associated key lengths used in the object to which the critical cryptographic parameters are associated. Note: These data objects may be in the form of data objects identified using an OID, and may include one or more algorithm specific parameters.

A few definitions and concepts (3/3) Cryptographic maintenance parameters: Critical cryptographic parameters together with a reference to a cryptographic maintenance policy. This means that cryptographic maintenance parameters shall include two components: critical cryptographic parameters, and an unambiguous reference to one cryptographic maintenance policy.

Basic operations The LTAS shall either accept to maintain the cryptographic validity of a record according to the cryptographic maintenance policy it supports, or refuse to accept the service. If it accepts, then it needs to perform the following basic operations: apply the cryptographic maintenance policy requested by the submitter within the cryptographic maintenance parameters and maintain the validity of the record according to that cryptographic maintenance policy using the critical cryptographic parameters that are present in the cryptographic maintenance policy associated with the archived record, periodically apply the original cryptographic maintenance policy that has been used in accordance with the critical cryptographic parameters, periodically apply a new cryptographic maintenance policy should the previous cryptographic maintenance policy become weak or inappropriate.

Conclusion Some meta-data created by the submitter shall allow to support cryptographic maintenance parameters. If a cryptographic maintenance policy is supported by the LTAS, then that meta-data shall be recognized and processed. There is the need to identify that kind of meta-data. There is then the need to define the internal structure of that meta-data.