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daniel
daniel
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As an extension to this quesiton, or this one how would you go about attacking a re used pad if the plaintext was randomized before being encrypted?

  0 0 0 1...         Plaintext

  0 1 1 1            seed(truly random number)
  0 1 0 1            Key1
  0 0 1 0            seed + Key1 mod 2 (=Cipher1)

  0 1 1 0...         Plaintext + PRNG(seed) mod 2 (=CipherR)
  1 10 1 10...         Key2(repeating 2 bit key "1 0") 
  1 01 0 10...         CipherR + Key2 mod 2 (=Cipher2) 

  0 0 1 0 1 01 0 10... Cipher1 & Cipher2 → ciphertext

This is using a OTP cipher to transmit the seed of a PRNG, then using a Vernam cipher with a repeating key to transmit the plaintext XORed with the PRN. Increasing the message length a little, hopefully to avoid cribbing.

How do you decode the Vernam cipher after the plain text has been randomized?

As an extension to this quesiton, or this one how would you go about attacking a re used pad if the plaintext was randomized before being encrypted?

  0 0 0 1...         Plaintext

  0 1 1 1            seed(truly random number)
  0 1 0 1            Key1
  0 0 1 0            seed + Key1 mod 2 (=Cipher1)

  0 1 1 0...         Plaintext + PRNG(seed) mod 2 (=CipherR)
  1 1 1 1...         Key2(repeating) 
  1 0 0 1...         CipherR + Key2 mod 2 (=Cipher2) 

  0 0 1 0 1 0 0 1... Cipher1 & Cipher2 → ciphertext

This is using a OTP cipher to transmit the seed of a PRNG, then using a Vernam cipher with a repeating key to transmit the plaintext XORed with the PRN. Increasing the message length a little, hopefully to avoid cribbing.

How do you decode the Vernam cipher after the plain text has been randomized?

As an extension to this quesiton, or this one how would you go about attacking a re used pad if the plaintext was randomized before being encrypted?

  0 0 0 1...         Plaintext

  0 1 1 1            seed(truly random number)
  0 1 0 1            Key1
  0 0 1 0            seed + Key1 mod 2 (=Cipher1)

  0 1 1 0...         Plaintext + PRNG(seed) mod 2 (=CipherR)
  1 0 1 0...         Key2(repeating 2 bit key "1 0") 
  1 1 0 0...         CipherR + Key2 mod 2 (=Cipher2) 

  0 0 1 0 1 1 0 0... Cipher1 & Cipher2 → ciphertext

This is using a OTP cipher to transmit the seed of a PRNG, then using a Vernam cipher with a repeating key to transmit the plaintext XORed with the PRN. Increasing the message length a little, hopefully to avoid cribbing.

How do you decode the Vernam cipher after the plain text has been randomized?

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daniel
daniel
  • 912
  • 5
  • 15

How to attack a two time pad if the plain text is randomized?

As an extension to this quesiton, or this one how would you go about attacking a re used pad if the plaintext was randomized before being encrypted?

  0 0 0 1...         Plaintext

  0 1 1 1            seed(truly random number)
  0 1 0 1            Key1
  0 0 1 0            seed + Key1 mod 2 (=Cipher1)

  0 1 1 0...         Plaintext + PRNG(seed) mod 2 (=CipherR)
  1 1 1 1...         Key2(repeating) 
  1 0 0 1...         CipherR + Key2 mod 2 (=Cipher2) 

  0 0 1 0 1 0 0 1... Cipher1 & Cipher2 → ciphertext

This is using a OTP cipher to transmit the seed of a PRNG, then using a Vernam cipher with a repeating key to transmit the plaintext XORed with the PRN. Increasing the message length a little, hopefully to avoid cribbing.

How do you decode the Vernam cipher after the plain text has been randomized?