What is a crib in code breaking?

The strategy of breaking a code by guessing at least part of the plaintext and then using that guess to deduce the encryption pattern is called a known-plaintext attack. The character sequence that you believe you know is called a crib.

How does known plaintext attack work?

Known plaintext attack is a scenario in which the attacker has access to pairs of known plaintexts and their corresponding ciphertexts. The goal is to guess the secret key (or a number of secret keys) or to develop an algorithm which would allow him to decrypt any further messages.

What is plaintext known as?

Information—a message, document, file, etc. —if to be communicated or stored in encrypted form is referred to as plaintext. Plaintext is used as input to an encryption algorithm; the output is usually termed ciphertext, particularly when the algorithm is a cipher.

How do Polyalphabetic ciphers work?

A polyalphabetic cipher is any cipher based on substitution, using multiple substitution alphabets. The encryption of the original text is done using the Vigenère square or Vigenère table. At different points in the encryption process, the cipher uses a different alphabet from one of the rows.

What was a crib in ww2?

The term crib was used at Bletchley Park to denote any known plaintext or suspected plaintext at some point in an enciphered message.

What is timing attack in cryptography?

In cryptography, a timing attack is a side-channel attack in which the attacker attempts to compromise a cryptosystem by analyzing the time taken to execute cryptographic algorithms. Information can leak from a system through measurement of the time it takes to respond to certain queries.

What is KPA in security?

The known-plaintext attack (KPA) is an attack model for cryptanalysis where the attacker has access to both the plaintext (called a crib), and its encrypted version (ciphertext). These can be used to reveal further secret information such as secret keys and code books.

What is Monoalphabetic?

Definition of monoalphabetic substitution : substitution in cryptography that uses a single substitution alphabet so that each plaintext letter always has the same cipher equivalent — compare polyalphabetic.

How do you break a Polyalphabetic cipher?

Once they know, for example, that every fifth letter in the encrypted message uses the same shift, they can break the code by solving five Caesar Ciphers in a row: shift every fifth letter backwards by 6, every sixth letter by 1, every seventh letter by 13 and so on.

What is crypto analysis?

Cryptanalysis is the process of studying cryptographic systems to look for weaknesses or leaks of information.