Method and system for verifying the identity of a communication partner
A method for verifying the identity of a communication partner, in particular in real-time communications, wherein a caller (A) sends a message towards a callee (B), and wherein the caller (A) attaches a self-signed certificate to the message, characterized in that the caller (A) and the callee (B) are part of a web-of-trust, wherein certificates of users within the web-of-trust are stored by one or more key-servers ( 3 ), wherein trust relationships between users within the web-of-trust are employed to compute a trust-chain between the caller (A) and the callee (B) based upon the certificate attached to the message and upon the callee's certificate, and wherein the further processing of the message received by the callee (B) is based on the length of the derived trust-chain. Furthermore, a corresponding system is described.
1. A method for verifying the identity of a communication partner in real-time, wherein a caller (A) sends a message towards a callee (B), and wherein the caller (A) attaches a self-signed certificate to said message, the method comprising:
storing, by one of more key-servers, certificates of users within a web-of-trust, wherein the caller (A) and the callee (B) are part of said web-of-trust, wherein the users upload the certificates which have been signed by other users to said one or more key-servers ( 3 ), wherein said one or more key-servers ( 3 ) include a specialized key-server ( 4 ) which verifies the signature in each said certificate it receives;
employing trust relationships between users within said web-of-trust to compute a trust-chain between the caller (A) and the callee (B) based upon the certificate attached to said message and upon the callee's certificate;
basing further processing of said message received by the callee (B) on the length of the derived trust-chain; and
said specialized key-server ( 4 ) periodically computing a file which contains the trust relationships among all the certificates verified by said specialized key-server.
2. Method according to claim 1 , wherein the caller (A) signs said message with its private key and appends the self-signed certificate containing a corresponding public key to said message.
3. Method according to claim 1 , wherein the trust relationships between users in said web-of-trust are derived at the time of the call in real-time or at least approximately in real-time.
4. Method according to claim 1 , wherein said file is periodically published by said specialized key-server ( 4 ).
5. Method according to claim 1 , wherein the periods of computing and/or publishing said file are dynamically adapted to the rate with which said specialized key-server ( 4 ) receives certificates.
6. Method according to claim 1 , wherein the trust relationships between verified certificates are contained in said file in a compressed, machine-readable format.
7. Method according to claim 1 , wherein the callee (B) accepts said message if the length of the derived trust-chain is below a predefined first threshold.
8. Method according to claim 1 , wherein the callee (B) rejects said message if the length of the derived trust-chain exceeds a predefined second threshold.
9. Method according to claim 1 , wherein the callee (B) invokes further steps to check the trustworthiness of said message if the length of the derived trust-chain exceeds a predefined third threshold.
10. Method according to claim 1 , wherein the employed web-of-trust is a PGP (Pretty Good Privacy) web-of-trust.
11. Method according to claim 1 , wherein filtering is deployed to confine the amount of pre-verified certificates.
12. Method according to claim 11 , wherein the confinement of pre-verified certificates is based on domains.
13. Method according to claim 1 , wherein the pre-verification process is distributed among several specialized key-servers ( 4 ).
14. A system for verifying the identity of a communication partner in real-time, wherein a caller (A) sends a message towards a callee (B), and wherein the caller (A) attaches a self-signed certificate to said message, the system comprising:
a web-of-trust of which the caller (A) and the callee (B) are part,
one or more key-servers ( 3 ) for storing certificates of users within said web-of-trust, said one or more key-servers ( 3 ) including a specialized key server ( 4 ) which is configured to verify signatures in each said certificate it receives and to periodically compute a file containing the trust relationships among all the certificates it stores,
an entity employing trust relationships between users within said web-of-trust to compute a trust-chain between the caller (A) and the callee (B) based upon the certificate attached to said message and upon the callee's certificate, and
a message processing element which is configured to perform further processing of said message received by the callee (B) based on the length of the derived trust-chain.
15. System according to claim 14 , wherein said one or more key-servers ( 3 ) constitute a key-server federation ( 2 ).
16. System according to claim 15 , wherein the key-servers ( 3 ) of said key-server federation ( 2 ) are configured to update each other's key-database.
17. System according to claim 14 , wherein said message processing element is configured to accept said message if the length of the derived trust-chain is below a predefined first threshold.
18. System according to claim 14 , wherein said message processing element is configured to reject said message if the length of the derived trust-chain exceeds a predefined second threshold.
19. System according to claim 14 , wherein said message processing element is configured to forward said message to a dedicated service for invoking further steps to check the trustworthiness of said message if the length of the derived trust-chain exceeds a predefined third threshold.
20. System according to claim 14 , wherein said specialized key-server is adapted to periodically publish the file.