Method for certifying public keys in a digital signature scheme

Claim 1

A method for certifying a user public key in a system having a first authority with a first public key of a digital signature scheme and a second authority with a second public key of a digital signature scheme, the method comprising the steps of: (a) presenting the user public key to the first authority for inspection of a given property; (b) if the user public key passes inspection of the first authority, causing the second authority to receive an indication that the user public key has passed inspection of the first authority; (c) having the second authority issue a compact certificate that indicates that the user public key possesses the given property, the compact certificate including a signature of the second authority but not including a public key of the first authority, wherein the compact certificate is equivalent to a conventional certificate containing the signature of the first authority, the public key of the first authority, and the public key of the second authority; and (d) storing information in order to keep at least the first authority accountable for pieces of data that the first authority contributes to certify.

Claim 2

A method for certifying a user public key in a system having a first authority with a first public key of a digital signature scheme and a second authority with a second public key of a digital signature scheme, the method comprising the steps of: (a) presenting the user public key to the first authority for inspection of a given property; (b) if the user public key passes inspection of the first authority, causing the second authority to receive an indication that the user public key has passed inspection of the first authority; (c) having the second authority issue a compact certificate that indicates that the user public key possesses the given property, the compact certificate including a signature of the second authority but not including a public key of the first authority, wherein the compact certificate is equivalent to a conventional certificate containing the signature of the first authority, the public key of the first authority, and the public key of the second authority; and (d) storing information in order to keep at least the first authority accountable for pieces of data that the first authority contributes to certify.

Claim 11

A method for certifying a user public key PK U where there are a plurality of authorities A l , . . . , A n that certify user public keys, where for each i<n, authority A i is configured to send authority A i+l authenticated messages that are verifiable by A i+l as having genuinely come from A i , and authority A n has a signing key SK n and an associated certified public key PK n , the method comprising the steps of: (a) having a verification key PK U presented to authority A l ; (b) having authority A l verify, by means of a predetermined procedure, that PK U possesses some properties out of a set of given properties; (c) for all i<n, having authority A i send authority A i+l a message indicating that PK U has been verified to possess the given properties; (d) issuing a compact certificate for PK U that includes a signature provided using SK n and does not include a public key of at least one authority A i for some j<n, wherein the compact certificate is equivalent to a conventional certificate containing the public key of A j ; and (e) storing accountability information that renders A j accountable for keys that A j contributes to certify.

Claim 12

A method for certifying a user public key PK U where there are a plurality of authorities A l , . . . , A n that certify user public keys, where for each i<n, authority A i is configured to send authority A i+l authenticated messages that are verifiable by A i+l as having genuinely come from A i , and authority A n has a signing key SK n and an associated certified public key PK n , the method comprising the steps of: (a) having a verification key PK U presented to authority A l ; (b) having authority A l verify, by means of a predetermined procedure, that PK U possesses some properties out of a set of given properties; (c) for all i<n, having authority A i send authority A i+l a message indicating that PK U has been verified to possess the given properties; (d) issuing a compact certificate for PK U that includes a signature provided using SK n and does not include a public key of at least one authority A i for some j<n, wherein the compact certificate is equivalent to a conventional certificate containing the public key of A j ; and (e) storing accountability information that renders A j accountable for keys that A j contributes to certify.