Re: Is there any way...

On Feb 27, 6:29 pm, "Studio Janck" <StudioJa...@xxxxxxxxx> wrote:
To get an encryption key from an encrypted file or string IF you have
the exact original? Is there a program that can "compare" them and
find out what the encryption key was?

Depends on the algorithm used. A simple stream cipher using a 32-bit
Linear Congruential Generator can be cracked with as little as 4 bytes
of known plaintext (if the LCG parameters are known). Simple
substitution ciphers can be cracked with enough plaintext using
frequency counts of characters. The German Enigma machine was cracked
using known plaintext during World War II.

Richard Mueller

.

Relevant Pages

  • Re: Is there any way...
    ... Is there a program that can "compare" them and ... find out what the encryption key was? ... A simple stream cipher using a 32-bit ... of known plaintext. ...
    (sci.crypt)
  • Re: quantum computing
    ... very fast (Shor's algorithm is one type of search). ... grover unstructured search algorithm is only a square root speedup, ... Nothing works against OTP since any message is a potentially valid mesage. ... once the entire plaintext is know it is possible to recover the key ...
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  • Re: How good an encryption algorithm is this?
    ... >> know both a plaintext and a ciphertext for some message ... This is pretty much what happens with any encryption algorithm that uses ... XOR alone. ...
    (microsoft.public.vc.language)