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You can prove that a document was signed after a certain date by including data that was not known to anyone before that date, such as stock market data. You cannot prove that a document was signed before a certain date by purely cryptographic means. Information doesn't go stale, so when you show a signature, it could have been signed at any time. You can ...


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Your diagram is not very clear, but XOR is not a good combiner function to use for timestamping, as it may allow backdating in some circumstances. For instance, see the "time travel" attacks in Section 3.3 of the following paper (e.g., pp.179-180): Cryptanalytic Attacks on Pseudorandom Number Generators. Depending upon how many inputs you have to the XOR ...


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The way a stream cipher works, traditionally, is that $E_k$ produces a pseudorandom bitstream (the keystream) based solely on the key $k$. The message is then encrypted by XORing the message with the keystream. This has a number of consequences, notably that if you know both the plaintext and ciphertext, it's trivial to compute the keystream (if $C=M\oplus ...


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I think that you're asking how to generate a timestamp response as defined in timestamp-protocol: RFC3161, with openssl to generate and sign the response using a PKCS#11 (HSM in your case) as a TSA signer. I think that there is no native way to use PKCS#11with openssl to do this. (maybe with some plugin like: opensc pkcs11 engine for openssl). If you take ...



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