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September 24, 2014

Alice and Bob and PGP Keys

By steve
3 Min read
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24September

Last week Alice and Bob showed how to cryptographically sign messages so that the recipient can be sure that the message came from the purported sender and hasn’t been forged by a third party. They can only do that if they can securely retrieve the senders public key – which means they need to retrieve it from the actual sender, rather than an impostor, and be sure it’s not...

September 19, 2014

Alice and Bob Sign Messages

By steve
6 Min read
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19September

Alice and Bob can send messages privately via a nosy postman, but how does Bob know that a message he receives is really from Alice, rather than from the postman pretending to be Alice? If they’re using symmetric-key encryption, and Bob is sure that he was talking to Alice when they exchanged keys, then he already knows that the mail is from Alice – as only he and Alice have the keys...

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