# Tag Info

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You're right — the autokey cipher described in the Wikipedia article is not self-synchronizing, since an error in one ciphertext letter will propagate through the decryption process into every $n$-th following plaintext letter, where $n$ is the key length. There are variants of the autokey cipher sometimes found in crypto puzzles that are self-synchronizing, ...

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Confusion arises because many people use the terms Vernam cipher and one-time pad interchangeably--but they are not the same thing. When young Gilbert Vernam, an AT&T research engineer, got his patent in 1919 (for a "Secret Signaling System"), Vernam cipher meant a fast encryption method using an additive stream cipher that was machine-based ...

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I think he is looking for difference of one time pad in vernam cipher and One Time Password (the 4/6/8) digit number which is used for transaction authentication) One Time Password: In OTP, the user gives his password w (more precisely a secret pass-phrase of at least 10 characters) to the OTP generator. The generator generates a random seed s which ...

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The Vernam Cipher is a One-Time Pad that was used on a paper-tape teletype machine, with 5-bit characters. That is, it's a specific implementation of a One-Time Pad, described in US Patent 1,310,719.

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Stream Ciphers A stream cipher produces key streams usually small sizes as bits (or bytes or words,...) that are x-ored with the message bits to produce the encrypted stream ( or call it the ciphertext). A stream cipher stores an internal state and updates it for the next output. They are also called state ciphers since the encryption depends on not only key ...

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Salsa20 is a PRF working in Counter-mode. That is it generates the keystream as $K_i=F_k(N,\text{Counter}_i)$. This Counter is a 64-bit value - not the nonce - thus allowing $2^{64}$ invocations of the PRF before repetition. Each PRF invocation yields 64 bytes, so in total $2^{64}\cdot 64=2^{70}$ bytes. Salsa20 generates the stream in 64-byte (512-bit) ...

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