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This entire article is utterly false and misconceived. It asserts that because "ONETIMEPAD" will be encrypted as "ONETIMEPAD" one time in 141167095653376, one t

by isaacg 11y ago

This entire article is utterly false and misconceived. It asserts that because "ONETIMEPAD" will be encrypted as "ONETIMEPAD" one time in 141167095653376, one time pads are not actually secure. The reason this is false is that just as often, "ONETIMEPAD" will be encrpted as "TWOTIMEPAD", or any other 10 letter string. Thus, the encryped string provides no information about the plain text, and so is perfectly encrypted. This article utterly wrong.

camperman 11y ago
I agree. The fallacy in his reasoning is here: "Let’s choose the very first key (in alphabetical order): AAAAAAAAAA. When we encrypt our plaintext of ONETIMEPAD with this key, we end up with a ciphertext of… ONETIMEPAD. Oops." Yeah, so what? He knows the plaintext already. An attacker doesn't and as you point out, there's nothing in the key that provides any information about the plaintext.
dragonwriter 11y ago
Yes. For a different illustration, sure, with the right key, a plaintext of "ATTACK US AT DAWN" will have a ciphertext of "ATTACK US AT DAWN". Which, you know, in isolation, sounds undesirable. But a ciphertext of "ATTACK US AT DAWN" will be equally likely (from an attacker's perspective, who has no advance knowledge of the plaintext content or the key) to correspond to a plaintext of "ATTACK US AT DUSK" or "ABORT US ATTACKS" or "DEFEND UK AT DUSK" or "LAUNCH FAST DRONE". (In fact, if you could guarantee that the ciphertext was never the plaintext, that would be an undesirable feature, because then if you knew the ciphertext and the encryption method without knowing the key or plaintext, you would learn information about the plaintext -- specifically, that it was not whatever the ciphertext was.)
- remram 11y ago
  In fact, the fact that a letter could not encrypt to itself was part of the weaknesses of the Enigma machines used by the Germans during WWII, which eventually led to its breakage.

by isaacg 11y ago

camperman 11y ago

I agree. The fallacy in his reasoning is here: "Let’s choose the very first key (in alphabetical order): AAAAAAAAAA. When we encrypt our plaintext of ONETIMEPAD with this key, we end up with a ciphertext of… ONETIMEPAD. Oops." Yeah, so what? He knows the plaintext already. An attacker doesn't and as you point out, there's nothing in the key that provides any information about the plaintext.

dragonwriter 11y ago

Yes. For a different illustration, sure, with the right key, a plaintext of "ATTACK US AT DAWN" will have a ciphertext of "ATTACK US AT DAWN". Which, you know, in isolation, sounds undesirable. But a ciphertext of "ATTACK US AT DAWN" will be equally likely (from an attacker's perspective, who has no advance knowledge of the plaintext content or the key) to correspond to a plaintext of "ATTACK US AT DUSK" or "ABORT US ATTACKS" or "DEFEND UK AT DUSK" or "LAUNCH FAST DRONE". (In fact, if you could guarantee that the ciphertext was never the plaintext, that would be an undesirable feature, because then if you knew the ciphertext and the encryption method without knowing the key or plaintext, you would learn information about the plaintext -- specifically, that it was not whatever the ciphertext was.)

remram 11y ago
In fact, the fact that a letter could not encrypt to itself was part of the weaknesses of the Enigma machines used by the Germans during WWII, which eventually led to its breakage.