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accepted What are the differences between a digital signature, a MAC and a hash?
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comment Can I use PGP to sign a message without providing cryptographic non-repudation?
If the sender uses a one-time signing key, how would this provide authentication at all? How would the recipient know that the one-time signing key is associated with the sender's validated master signing key?
Dec
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comment Can I use PGP to sign a message without providing cryptographic non-repudation?
If understand correctly, an MDC provides some level of integrity, but not authentication. After all, even with an MDC, an attacker could just use the recipient's public key to create a new encrypted message. What I'm asking for is authentication without non-repudiation. I realise the non-repudiation OpenPGP offers isn't good enough for court, but it could be good enough for another OpenPGP user.
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comment What are the differences between a digital signature, a MAC and a hash?
@PaĆ­loEbermann: that's perfect, thanks! Your edit was substantial so I enabled "community wiki" on my answer, it's only fair.
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comment What are the differences between a digital signature, a MAC and a hash?
Please go ahead and edit it to make it look less homework, I'm not sure what I'm doing wrong so I'm not sure I can fix it. Thanks @PaĆ­loEbermann! I posted this question because I saw some users confuse these three primitives in this question, and I wanted a question like this to point to.
Dec
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comment Can I use PGP to sign a message without providing cryptographic non-repudation?
@AJ Henderson: you're right. Thanks for the explanation!
Dec
10
comment Can I use PGP to sign a message without providing cryptographic non-repudation?
@AJ Henderson - That would provide non-repudiation, which is an undesired property. The recipient can pass Encrypt(symmetric_key, (message, mac)) and Encrypt(public_key, Sign(private_key, symmetric_key)) to a third party, and the third party can be confident the message originated from the sender, since the recipient could not have forged it.
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