Patent ID: 7493661

Claim:
A method for recovering lost keys in a public key encryption system that includes a central key repository and a plurality of users, where a user's public key is stored at the central key repository and user's associated private key is stored locally on a user's computer, the method comprising: designating a recovery question and an answer to the recovery question; encrypting the user's private key using a first hash of the answer as a session key in a symmetric key encryption process; hashing the answer a predetermined number of times to generate a second hash of the answer; storing the second hash and the recovery question at the central key repository without exposing the answer to the recovery question to the central key repository; and when prompted by the user to recover a lost private key: receiving the answer; hashing the answer the predetermined number of times to generate a third hash and transmitting the third hash to the central key repository without transmitting the answer itself; comparing the second and third hashes; if the second and third hashes match, returning the encrypted private key to the user; and decrypting the private key using the first hash and storing the private key.