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The Cryptographic Token Key Initialization Protocol (CT-KIP)

The Cryptographic Token Key Initialization Protocol (CT-KIP). OTPS Workshop February 2006. CT-KIP Primer. A client-server protocol for initialization (and configuration) of cryptographic tokens with shared keys

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The Cryptographic Token Key Initialization Protocol (CT-KIP)

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  1. The Cryptographic Token Key Initialization Protocol (CT-KIP) OTPS Workshop February 2006

  2. CT-KIP Primer • A client-server protocol for initialization (and configuration) of cryptographic tokens with shared keys • Intended for general use within computer and communications systems employing connected cryptographic tokens • Objectives • To provide a secure and interoperable method of initializing cryptographic tokens with secret keys • To provide a solution that is easy to administer and scales well • To provide a solution which does not require private-key capabilities in tokens, nor the existence of a public-key infrastructure

  3. Current status • Version 1.0 finalized in December 2005 • Describes a 4-pass protocol for the initialization of cryptographic tokens with secret keys • Includes a public-key variant as well as a shared-key variant

  4. Client Hello Server Hello Client Nonce Server Finished Principle of Operation (4-pass variant) CT-KIP server CT-KIP client

  5. CT-KIP 1- and 2-pass • New variants introduced in January draft • To meet the needs of certain environments • E.g. no communication path token  server, or high network latency • Essentially key transport or key wrap • Maintain the property that No other entity than the token and the server will have access to generated / distributed keys

  6. Client Hello Server Hello Client Nonce Server Finished CT-KIP 2-pass CT-KIP server CT-KIP client

  7. CT-KIP 2-pass • New extension in ClientHello signals support for two-pass, and supported key transport/key wrapping schemes • Payload could include a token public key • Client includes nonce in ClientHello • Will ensure Server is alive • Server provides key wrapped (in symmetric key or token’s public key) in new extension in ServerFinished

  8. Client Hello Server Hello Client Nonce Server Finished CT-KIP 1-pass CT-KIP server CT-KIP client

  9. CT-KIP 1-pass • Server MUST have a priori knowledge of token’s capabilities • Server provides key wrapped in symmetric key or token’s public key in new extension in ServerFinished

  10. Cryptographic properties • Server authentication through MAC in ServerFinished if dedicated K_auth • Otherwise MAC provides key confirmation • With K_auth no key confirmation • Server aliveness through MAC on client nonce • Not present in 1-pass, however

  11. Identified Issues • Key confirmation • Present in 4-pass version • Shall it be required for 1-, 2-pass? • Requires some more work for 1-pass • Replay protection • OK in 2- and 4-pass • Method to use in 1-pass? Counter? • Will require some additional capabilities in token, see mailing list discussion

  12. Next Steps • Decide on key confirmation, replay protection • Resolve any other comments • Produce new draft version • Preferably within 4 – 5 weeks

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