Privacy-enhanced e-passport authentication protocol
A passport authentication protocol provides for encryption of sensitive data such as biometric data and transfer of the encryption key from the passport to the authentication authority to permit comparison to a reference value.
1. A method of transferring information stored in a machine readable document pertaining to a correspondent to a machine for examination, said information including a sensitive portion to be kept confidential during transmission, comprising the steps of:
assembling at said correspondent a message having a primary portion M 1 containing said sensitive portion of said information retrieved from said machine readable document, and a secondary portion M 2 containing less sensitive portion of said information and including a long term public key of said correspondent,
generating an encryption key e from a session private key and said long term public key of the correspondent,
encrypting said primary portion with said encryption key e to obtain a ciphertext C,
combining said ciphertext C and said secondary portion M 2 and generating a signature component s of said correspondent from said combination,
transferring said signature component s, said ciphertext C and said secondary portion of M 2 to the machine, said machine
generating a value from said signature component s, said ciphertext C and said secondary portion M 2 , generating an ephemeral private key, and utilizing said value and said ephemeral private key to generate a public session key from said value and said ephemeral private key,
forwarding said public session key to said correspondent and obtaining from said correspondent a further public key to permit recovery of said encryption key e, and
said machine recovering said primary portion M 1 from said ciphertext C using said encryption key e.
2. A method according to claim 1 wherein said machine readable document is a passport and said machine is a verifier of said passport.
3. A method according to claim 2 wherein said primary portion M 1 contains biometric information and said machine compares said biometric information to a reference input.
4. A method according to claim 1 , wherein said ciphertext C and said secondary portion M 2 are combined by hashing to obtain a hash h.
5. A method according to claim 4 wherein said signature component s is obtained from a combination of a long term private key d of said correspondent, a private session key k and said hash h.
6. A method according to claim 5 wherein said private session key k is used to generate said encryption key e.
7. A method according to claim 6 wherein said private session key k and said long term public key are used to generate said encryption key e.
8. A method according to claim 1 , further comprising checking redundancy of the primary portion and adding additional data to the primary portion prior to encrypting said primary portion if redundancy is below a pre-determined level of redundancy.