Email verification

1. Method for verifying an identity of an email-address utilized by a client device, the method being performed by a server and comprising:

receiving a request for verifying the identity of the email-address;

generating a first asymmetric key pair, KP1-S, comprising a private key, PrivK1-S, and a public key, PubK1-S;

calculating a first verification token, VN-1, based on the private key, PrivK1-S, of KP1-S and a known public key, PubK-C, of an asymmetric key pair, KP-C, of the client device;

transmitting a verification email message to the email-address to be verified comprising the public key, PubK1-S, of KP1-S;

receiving a response to the verification email message including a second verification token, VN-2, calculated by the client device based on the private key, PrivK-C, of KP-C and the public key, PubK1-S, transmitted in the verification email message;

verifying the identity of the email-address by verifying that VN-2 is identical to VN-1.

2. The method of claim 1 , wherein the verification tokens, VN-1 and VN-2, are calculated based on a Diffie-Hellman key exchange method, in particular based on an elliptic curve Diffie-Hellman key exchange method.

3. The method of claim 1 , wherein the public key PubK1-S is comprised in the header of the verification email message.

4. The method of claim 1 , wherein the identity of the email address is verified only for a given amount of time before expiration.

5. The method of claim 1 , wherein the communication between the server and the client device is performed as signed communication, wherein the server signs its communication by a private key, PrivK2-S, of a second asymmetric key pair, KP2-S, of the server, and

wherein the server verifies the received communication of the client device by the known public key PubK-C.

6. The method of claim 1 , wherein the method further comprises issuing a certificate in response to verifying that VN-1 is identical to VN-2.

7. The method of claim 1 , wherein the method further comprises deleting the first asymmetric key pair KP1-S by the server in response to the verification email being transmitted to the email-address to be verified.

8. The method of claim 1 , wherein the communication between the server and the client device is encrypted.

9. Method for verifying an email-address utilized by a client device, the method being performed by the client device and comprising:

receiving a verification email message comprising a public key, PubK1-S, of a first asymmetric key pair, KP1-S, of a server, wherein the verification email message is received by the email-address to be verified;

calculating a verification token, VN-2, based on a private key, PrivK-C, of an asymmetric key pair, KP-C, of the client device and the public key PubK1-S received in the verification email message;

transmitting the verification token VN-2 to the server.

10. The method of claim 8 , wherein calculating and transmitting the verification token VN-2 are performed automatically.

11. The method of claim 9 , further comprising extracting the public key PubK1-S from a header of the received verification email message.

12. Server for verifying an identity of an email-address utilized by a client device, adapted to:

receive a request for verifying the identity of the email-address;

generate a first asymmetric key pair, KP1-S, comprising a private key, PrivK1-S, and a public key, PubK1-S;

calculate a first verification token, VN-1, based on the private key, PrivK1-S, of KP1-S and a known public key, PubK-C, of an asymmetric key pair, KP-C, of the client device;

transmit a verification email message to the email-address to be verified comprising the public key, PubK1-S, of KP1-S;

receive a response to the verification email message including a second verification token, VN-2, calculated by the client device based on a private key, PrivK-C, of KP-C and the public key, PubK1-S, transmitted in the verification email message;

verify the identity of the email-address by verifying that VN-2 is identical to VN-1.

13. The server of claim 12 further to calculate the verification tokens, VN-1 and VN-2, based on a Diffie-Hellman key exchange method, in particular based on an elliptic curve Diffie-Hellman key exchange method.

14. The server of claim 12 further to include the public key PubK1-S in the header of the verification email message.

15. The server of claim 12 further to cause verification of the identity of the email address only for a given amount of time before expiration.

16. Client device for verifying an identity of an email-address utilized by the client device, adapted to:

receive a verification email message comprising a public key, PubK1-S, of a first asymmetric key pair, KP1-S, of a server, wherein the verification email message was transmitted to the email-address to be verified;

calculate a verification token, VN-2, based on a private key, PrivK-C, of an asymmetric key pair, KP-C, of the client device and the public key PubK1-S received in the verification email message;

transmit the verification token VN-2 to the server.

17. Method for verifying an identity of an email-address utilized by a client device, comprising:

receiving, at a server, a request for verifying the identity of the email-address;

generating, at the server, a first asymmetric key pair, KP1-S, comprising a private key, PrivK1-S, and a public key, PubK1-S,

calculating, at the server, a first verification token, VN-1, based on the private key, PrivK1-S, of KP1-S and a known public key, PubK-C, of an asymmetric key pair, KP-C, of the client device;

transmitting, from the server to the email-address to be verified, a verification email message comprising the public key, PubK1-S, of KP1-S;

receiving, at the client device, the verification email message;

calculating, at the client device, a second verification token, VN-2, based on a private key, PrivK-C, of the key pair KP-C and the public key PubK1-S received in the verification email message;

transmitting, from the client device to the server, the verification token VN-2;

verifying, at the server, the identity of the email-address by verifying that VN-2 is identical to VN-1.

18. System for verifying an identity of an email-address utilized by a client device, the system comprising the client device and a server and being adapted to

receive, at the server, a request for verifying the identity of the email-address;

generate, at the server, a first asymmetric key pair, KP1-S, comprising a private key, PrivK1-S, and a public key, PubK1-S,

calculate, at the server, a first verification token, VN-1, based on the private key, PrivK1-S, of KP1-S and a known public key, PubK-C, of an asymmetric key pair, KP-C, of the client device;

transmit, from the server to the email-address to be verified, a verification email message comprising the public key, PubK1-S, of KP1-S;

receive, at the client device, the verification email message;

calculate, at the client device, a second verification token, VN-2, based on a private key, PrivK-C, of the key pair KP-C and the public key PubK1-S received in the verification email message;

transmit, from the client device to the server, the verification token VN-2;

verify, at the server, the identity of the email-address by verifying that VN-2 is identical to VN-1.

19. Computer program product for verifying an identity of an email-address utilized by a client device, the computer program product comprising:

a non-transitory computer-readable storage medium; and

program code stored on the non-transitory computer-readable storage medium that, when executed by one or more server processors, causes the one or more server processors to:

receive a request for verifying the identity of the email-address;

generate a first asymmetric key pair, KP1-S, comprising a private key, PrivK1-S, and a public key, PubK1-S;

calculate a first verification token, VN-1, based on the private key, PrivK1-S, of KP1-S and a known public key, PubK-C, of an asymmetric key pair, KP-C, of the client device;

transmit a verification email message to the email-address to be verified comprising the public key, PubK1-S, of KP1-S;

receive a response to the verification email message including a second verification token, VN-2, calculated by the client device based on the private key, PrivK-C, of KP-C and the public key, PubK1-S, transmitted in the verification email message;

verify the identity of the email-address by verifying that VN-2 is identical to VN-1.

20. Computer program product for verifying an identity of an email-address utilized by a client device, the computer program product comprising:

a non-transitory computer-readable storage medium; and

program code stored on the non-transitory computer-readable storage medium that, when executed by one or more client processors, causes the one or more client processors to:

receive a verification email message comprising a public key, PubK1-S, of a first asymmetric key pair, KP1-S, of a server, wherein the verification email message is received by the email-address to be verified;

calculate a verification token, VN-2, based on a private key, PrivK-C, of an asymmetric key pair, KP-C, of the client device and the public key PubK1-S received in the verification email message;

transmit the verification token VN-2 to the server.