To unblind the received signature of the message-signature pair, the requester A first takes the blind signature S, the previously generated message digest m, the private key [n.sub.A], and the public key [PK.sub.B] of the signer to extract the blinded signature S' as expressed by (23).
After receiving the message-signature tuple (S', m , R, [bar.C], K), the verifier T uses the signer's public key [PK.sub.B] to verify the authentication of the alleged signature and the passing message digest by checking whether (25) holds.
The message digest
is a well-known cryptographic assumption: the secure one way hash function has properties such that given a message m, it is easy to compute H(m).
(3) When [MAG.sub.2] received the request of encrypted authentication, it first checks the message digest for message integrity.
(5) When MR receives the reply, MR checks message digest (H([E.sub.K]([M.sub.4]) [parallel] [MAC.sub.MAG2])) and uses K key to decrypt the encrypted message.
* The recipient, Bob, can only decrypt the message digest
using Alice's public key, thereby verifying that Alice sent the message--assuming that the public key is correctly associated with Alice.
It then decrypts the encrypted message digest (and date-time stamp) using the sender's public key.
First, the identity of the sender is authenticated because, as mentioned above, successful decryption using the sender's public key verifies that the message digest was encrypted using the sender's private key, which presumably is used only by the sender.
A more advanced use of fingerprinting is found in RSA Data Security's use of message digests
for authentication purposes.
Typical methods involve computing a message digest
of the message to be signed, then passing the digest through a public key encryption algorithm using the private key of the signing individual.
His topics include the language of cryptography, components, hashing and message digests
, cryptanalysis and code breaking, public key infrastructure, steganography, and quantum cryptography.
Authentication is most often achieved through challenge and response, digital certificates, or message digests
and digital signatures.