Receiver non-repudiation

A machine-implemented method to execute on a proxy, comprising:

• encrypting, by the proxy, data designated for a receiver;
• generating, by the proxy, a global identifier for a decrypted version of the encrypted data;
• sending, by the proxy, the encrypted data and the global identifier to the receiver;
• receiving, by the proxy, a signature from the receiver representing a hashed value for portions of information associated with the global identifier and the encrypted data, the hashed value is encrypted with a private key and a policy informs the receiver how to establish the signature from the portions of information, receipt of the signature indicating the receiver has the encrypted data and the global identifier;
• transmitting, by the proxy, a key to decrypt the encrypted data to the receiver;
• and
• determining, by the proxy, when the key is received by the receiver by comparing a different signature received back from the receiver with an independently generated value to determine whether the receiver successfully received the key to decrypt the encrypted data, the different signature supplied by the receiver including a hash of the key and a hash of the decrypted version of the encrypted data.