Recipients can then compute their own hash of the document, decrypt the attached, encrypted hash using my public key, and compare the results. If the hashes match, the document is good, and non- repudiation has been established since it was encrypted with MY private key.
To extend our discussion, suppose I wish to send an encrypted message to multiple recipients. I would then encrypt the (randomly generated) symmetric key to each recipient's public key in turn. All of the encrypted copies (of the symmetric key) are attached. A valid recipient will be able to encrypt his (and only his) copy of the symmetric key and then decrypt the document.
On Jun 20, 2007, at 11:30 AM, Newton Hammet wrote:
I am not exactly sure how the sig fits in but it is a hash value of either the original message or the encrypted message depending on the order of signing and encryption. This hash is encrypted with sender's private keypart of his own public key. This part I am not sure of so others can correct me if I am wrong with this part. I believe signatures are encrypted with private key and decrypted withpublic key. In order to protect against some exploits it is best to have your public key consist of one signing key and a different key for messageencryption. -Newton
smime.p7s
Description: S/MIME cryptographic signature
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