Authenticating a system based on a certificate

1. A method performed by a receiver system, the method comprising:

receiving a certificate that identifies a sender system as owning a domain;

determining that a signature in the certificate is insufficient to validate the certificate, the determining based on the signature having been signed by a certificate authority with whom the receiver system does not have a trust relationship or the signature having been self-signed by the sender system;

in response to determining that the signature is insufficient to validate the certificate, sending an electronic message to the domain identified in the certificate, the electronic message sent via a mail exchange network, wherein the mail exchange network correlates the domain to an address that a true owner of the domain has registered with a mail exchange authority;

receiving a response from the address that the mail exchange network correlates to the domain, the response indicating that the certificate is associated with the true owner of the domain; and

validating the certificate as trusted and authenticating the sender system as the true owner of the domain based on the response.

2. The method of claim 1 , wherein:

the certificate includes a public key;

the electronic message to the domain identified in the certificate contains a secret message encrypted using the public key;

the response from the address that the mail exchange network correlates to the domain contains the secret message as decrypted by the domain; and

authenticating the sender system as the true owner of the domain comprises verifying the decrypted secret message.

3. The method of claim 2 , wherein the certificate indicates a time period during which the certificate is valid.

4. The method of claim 2 , wherein the secret message as decrypted by the domain is received within a predetermined period of time.

5. The method of claim 2 , further comprising provisioning encryption services for the domain as a result of authenticating the sender system as the true owner of the domain.

6. The method of claim 2 , further comprising determining that the secret message as decrypted by the domain is not received within a predetermined period of time and, in response, resending the encrypted secret message to the domain identified in the certificate.

7. The method of claim 2 , further comprising determining that the secret message as decrypted by the domain is not received within a predetermined period of time and, in response, determining that ownership of the domain is to remain available for authentication.

8. The method of claim 1 , further comprising:

after authenticating the sender system as the true owner of the domain, receiving a request to authenticate a different sender system as the true owner of the domain; and

denying the request to authenticate the different sender system as the true owner of the domain based on having already authenticated the original sender system as the true owner of the domain.

9. A receiver system, comprising:

at least one processor and at least one storage device, the at least one processor, in conjunction with the at least one storage device, configured to cause the receiver system to:

receive a certificate that identifies a sender system as owning a domain;

determine that a signature in the certificate is insufficient to validate the certificate, the determination based on the signature having been signed by a certificate authority with whom the receiver system does not have a trust relationship or the signature having been self-signed by the sender system;

in response to determining that the signature is insufficient to validate the certificate, send an electronic message to the domain identified in the certificate, the electronic message sent via a mail exchange network, wherein the mail exchange network correlates the domain to an address that a true owner of the domain has registered with a mail exchange authority; and

determine whether to validate the certificate as trusted and authenticate the sender system as the true owner of the domain based at least in part on whether a response indicating that the certificate is associated with the true owner of the domain has been received from the address that the mail exchange network correlates to the domain.

10. The receiver system of claim 9 , wherein:

the certificate includes a public key;

the electronic message to the domain identified in the certificate contains a secret message encrypted using the public key;

the response from the address that the mail exchange network correlates to the domain contains the secret message as decrypted by the domain; and

authenticating the sender system as the true owner of the domain comprises verifying the decrypted secret message.

11. The receiver system of claim 10 , wherein the certificate indicates a time period during which the certificate is valid.

12. The receiver system of claim 10 , wherein the secret message as decrypted by the domain is received within a predetermined period of time.

13. The receiver system of claim 10 , the at least one processor further configured to cause the receiver system to, as a result of authenticating the sender system as the true owner of the domain, provision encryption services for the domain.

14. The receiver system of claim 10 , the at least one processor further configured to cause the receiver system to determine that the secret message as decrypted by the domain is not received within a predetermined period of time and, in response, resend the encrypted secret message to the domain identified in the certificate.

15. The receiver system of claim 10 , the at least one processor further configured to cause the receiver system to determine that the secret message as decrypted by the domain is not received within a predetermined period of time and, in response, determine that ownership of the domain is to remain available for authentication.

16. The receiver system of claim 9 , the at least one processor further configured to cause the receiver system to:

after authenticating the sender system as the true owner of the domain, receive a request to authenticate a different sender system as the true owner of the domain; and

deny the request to authenticate the different sender system as the true owner of the domain based on having already authenticated the original sender system as the true owner of the domain.

17. A non-transitory computer readable medium comprising logic that, when executed by one or more processors, is operable to:

receive a certificate that identifies a sender system as owning a domain;

determine that a signature in the certificate is insufficient to validate the certificate, the determination based on the signature having been signed by a certificate authority with whom the receiver system does not have a trust relationship or the signature having been self-signed by the sender system;

in response to determining that the signature is insufficient to validate the certificate, send an electronic message to the domain identified in the certificate, the electronic message sent via a mail exchange network, wherein the mail exchange network correlates the domain to an address that a true owner of the domain has registered with a mail exchange authority;

receive a response from the address that the mail exchange network correlates to the domain, the response indicating that the certificate is associated with the true owner of the domain; and

validate the certificate as trusted and authenticate the sender system as the true owner of the domain based on the response.

18. The computer readable medium of claim 17 , wherein:

the certificate includes a public key;

the electronic message to the domain identified in the certificate contains a secret message encrypted using the public key;

the response from the address that the mail exchange network correlates to the domain contains the secret message as decrypted by the domain; and

authenticating the sender system as the true owner of the domain comprises verifying the decrypted secret message.

19. The computer readable medium of claim 18 , wherein the certificate indicates a time period during which the certificate is valid.

20. The computer readable medium of claim 18 , wherein the secret message as decrypted by the domain is received within a predetermined period of time.

21. The computer readable medium of claim 18 , the logic further operable to, as a result of authenticating the sender system as the true owner of the domain, provision encryption services for the domain.

22. The computer readable medium of claim 18 , the logic further operable to determine that the secret message as decrypted by the domain is not received within a predetermined period of time and, in response, resend the encrypted secret message to the domain identified in the certificate.

23. The computer readable medium of claim 18 , the logic further operable to determine that the secret message as decrypted by the domain is not received within a predetermined period of time and, in response, determine that ownership of the domain is to remain available for authentication.

24. The computer readable medium of claim 17 , the logic further operable to:

after authenticating the sender system as the true owner of the domain, receive a request to authenticate a different sender system as the true owner of the domain; and

deny the request to authenticate the different sender system as the true owner of the domain based on having already authenticated the original sender system as the true owner of the domain.