Patent ID: 7360080

Claim:
A method for establishing a pseudonym system by having a certificate authority accepting a user as a new participant in said pseudonym system, the method comprising the steps of: receiving a first public key provided by said user; verifying that said user is allowed to join the system; computing a credential by signing the first public key using a secret key owned by said certificate authority; and publishing said first public key and said credential, wherein the step of receiving a first public key further includes receiving an external public key being registered for said user with an external public key infrastructure and receiving an encryption of a secret key encrypted by using said first public key; the step of verifying that said user is allowed to join the system further includes verifying that said external public key is indeed registered with said external public key infrastructure; the step of publishing said first public key and said credential comprises publishing said encryption and the name of the external public key infrastructure; and additionally comprises the step of proving that the secret key corresponding to said external public key is encrypted in said received encryption.