The GPG secure mailing system uses both RSA and a symmetric cipher. When one installs GPG, the software generates two large (2048 bits or so) numbers, to produce a modulus of 1024 bits. Such a number is too large to be factored easily. The private and public keys are generated from these quantities. The private key is enciphered with a symmetric cipher using a usersupplied pass phrase as the key. To send a message, a symmetric key is randomly generated, and the message enciphered using the symmetric with that key; the key is enciphered using the recipient’s public key, and the message and enciphered key are sent.

ECS 153, Computer Security Version of May 27, 2021 at 11:42PM

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