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CBC-R [8] turns a decryption oracle into an encryption oracle, and is primarily demonstrated against padding oracles. Using padding oracle attack CBC-R can craft an initialization vector and ciphertext block for any plaintext: decrypt any ciphertext P i = PODecrypt( C i) ⊕ C i−1, select previous cipherblock C x−1 freely,
CBC decryption example with a toy 2-bit cipher CBC has been the most commonly used mode of operation. Its main drawbacks are that encryption is sequential (i.e., it cannot be parallelized), and that the message must be padded to a multiple of the cipher block size.
The attacker can then combine the oracle with a systematic search of the problem space to complete their attack. [1] The padding oracle attack, and compression oracle attacks such as BREACH, are examples of oracle attacks, as was the practice of "crib-dragging" in the cryptanalysis of the Enigma machine. An oracle need not be 100% accurate ...
For CBC ciphertext stealing, there is a clever (but opaque) method of implementing the described ciphertext stealing process using a standard CBC interface. Using this method imposes a performance penalty in the decryption stage of one extra block decryption operation over what would be necessary using a dedicated implementation.
It makes some of the plaintext structure visible in the ciphertext. Selecting other modes, such as using a sequential counter over the block prior to encryption (i.e., CTR mode) and removing it after decryption avoids this problem. Another mode, Cipher Block Chaining (CBC) is one of the most commonly used modes of AES due to its use in TLS. CBC ...
The oracle returns the bitwise exclusive-or of the key with the string of zeroes. The string returned by the oracle is the secret key. While the one-time pad is used as an example of an information-theoretically secure cryptosystem, this security only holds under security definitions weaker than CPA security. This is because under the formal ...
The term "crib" originated at Bletchley Park, the British World War II decryption operation, where it was defined as: A plain language (or code) passage of any length, usually obtained by solving one or more cipher or code messages, and occurring or believed likely to occur in a different cipher or code message, which it may provide a means of ...
A deterministic encryption scheme (as opposed to a probabilistic encryption scheme) is a cryptosystem which always produces the same ciphertext for a given plaintext and key, even over separate executions of the encryption algorithm.