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While transposition ciphers may move bits around, they are entirely linear; and effectively perform substitution... except the data positions are substituted, instead of the values. Let's say I have the ciphertext raspberry and I encrypt it to get bsapryrre Statistical analysis becomes even easier than with a substitution cipher: I simply look for a word or ...


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If I can prove there's no single key that can encrypt to both outputs I can prove with 100% certainty which message it is, but if not I can't. "pqrs" or "jmlo" You can identify which password it is by comparing each letter with the corresponding letter once encrypted. For example, compare $P-R$ with $J-L$ (treating each letter as a ...


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I'm guessing from your description that you are describing a mode of operation where $A$ is the message and $B$ is an IV/nonce for a specific block. However you seem to have made an exception where the attacker can know the ciphertext both with and without the $B$ involved. As such, you have a rather weird use of the cipher. To generalize to an arbitrary ...


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The approach in the Heys’ tutorial where the author uses the approach bruteforce last round using every possible keybit [at the output of] active sboxes and trace differentials up to [the output of] $r-1$ rounds is more fundamental because it is more general. One needs to meet in the middle at the output of some round and check which value for the guessed ...


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I am curious which security algorithms are sensitive to an attacker being able to encrypt whatever they choose to (and see the result). No algorithm would be considered secure if they could be broken under that assumption. Also, is there a known guide (or a googleable name) of this property of crypto algorithms? There's a couple of different names (based ...


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This is called a Chosen Plaintext Attack (or CPA for short) where the attacker can obtain the ciphertext for arbitrary plaintext. A modern cipher should be CPA-resistant. For example, AES-CBC with a proper random IV is IND-CPA. But be aware that there are many other types of security levels, CPA is just one of them. You can find a good overview of crypto ...


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Let's consider what you know: you have the last block, the IV, and the entire ciphertext. What you don't know is the key or the plaintext. Since CBC-mode encryption uses the IV directly only with the first block you must find the first block, before the IV even becomes useful for your attack. Since the CBC mode uses AES(plaintext[i] XOR ciphertext[i-1], key) ...


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Usually, the brute-force attack is performed with known-plaintext where a message $m$ and its ciphertext $c = \operatorname{XTEA}(k,m)$ is available. Indeed, one may need more than one to exactly found the key since a key selects permutation and at the point $m$ there can be more than one permutation selected by different keys that maps to the same ...


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