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dhbitty is a small public key encryption program written in C. It uses elliptic curve Diffie-Hellman in the form of Curve25519 to establish a shared secret between two users, and uses that secret to symmetrically encrypt and authenticate messages. There are no private key files; only passphrases. Never lose that pesky thing again. Both the sender and the receiver can decrypt a message. In fact, there is no distinction between sender and receiver. Both passphrases must be strong. There is no signing. A similarly useful form of authentication occurs using only DH. dhbitty attempts to be as simple as possible. It is not optimized, but achieves a comfortable speed for most uses. It does not use floating point numbers, or integers longer than 32 bits. It does not contain more algorithms than are needed. Example This is how Alice generates her public key with dhbitty: $ dhbitty generate alice_public_key.txt username:passphrase (this is visible!): alice:Keyfiles be damned! Done. Bob will do the same thing: $ dhbitty generate bob_public_key.txt username:passphrase (this is visible!): bob:Bob's Spectacular Passphrase Done. Alice will publish her alice_public_key.txt, and Bob will publish his bob_public_key.txt. They can now access each other's public keys. (But they should be careful that Eve cannot surreptitiously replace either public key with her own!) Alice wants to send files to Bob. She packages them into a .tar archive (or any other type of archive with timestamps), along with her message. Then she uses dhbitty: $ dhbitty encrypt bob_public_key.txt files_to_bob.tar files_to_bob.tar.dhbt username:passphrase (this is visible!): alice:Keyfiles be damned! Done. Alice sends files_to_bob.tar.dhbt to Bob. Bob will use dhbitty to decrypt this archive: $ dhbitty decrypt files_to_bob.tar.dhbt files_to_bob.tar username:passphrase (this is visible!): bob:Bob's Spectacular Passphrase This is the public key of file's secondary owner: 0002f02b318c307bac07f3148a33c975cea04b79a870f0a5c7771cd38cc1986e Done. Bob can verify that the public key dhbitty just gave him indeed is Alice's public key. He unpacks the now-decrypted archive to access the files Alice sent to him. In practice, Alice and Bob should use a system like diceware to pick passphrases, in order to be confident of their strength. Seven words picked using diceware is a good choice.
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@comment $NetBSD: PLIST,v 1.1.1.1 2012/08/11 17:43:46 agc Exp $
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bin/dhbitty
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share/doc/dhbitty/dhbitty.html
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