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In cryptography, ciphertext or cyphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. [1] Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext that is unreadable by a human or computer without the proper cipher to decrypt it.
In cryptography, a ciphertext-only attack (COA) or known ciphertext attack is an attack model for cryptanalysis where the attacker is assumed to have access only to a set of ciphertexts. While the attacker has no channel providing access to the plaintext prior to encryption, in all practical ciphertext-only attacks, the attacker still has some ...
An example implementation of this method can be found on iOS devices, where the cryptographic key is kept in a dedicated 'effaceable storage'. [27] Because the key is stored on the same device, this setup on its own does not offer full privacy or security protection if an unauthorized person gains physical access to the device.
For example, diffusion ensures that any patterns in the plaintext, such as redundant bits, are not apparent in the ciphertext. [3] Block ciphers achieve this by "diffusing" the information about the plaintext's structure across the rows and columns of the cipher.
In a known-plaintext attack, Eve has access to a ciphertext and its corresponding plaintext (or to many such pairs). In a chosen-plaintext attack, Eve may choose a plaintext and learn its corresponding ciphertext (perhaps many times); an example is gardening, used by the British during WWII.
Sometimes these implications go in both directions, making two definitions equivalent; for example, it is known that the property of indistinguishability under adaptive chosen-ciphertext attack (IND-CCA2) is equivalent to the property of non-malleability under adaptive chosen-ciphertext attack (NM-CCA2). This equivalence is not immediately ...
For example, when cribs were lacking, Bletchley Park would sometimes ask the Royal Air Force to "seed" a particular area in the North Sea with mines (a process that came to be known as gardening, by obvious reference). The Enigma messages that were soon sent out would most likely contain the name of the area or the harbour threatened by the mines.
The cipher illustrated here uses a left shift of 3, so that (for example) each occurrence of E in the plaintext becomes B in the ciphertext. In cryptography , a Caesar cipher , also known as Caesar's cipher , the shift cipher , Caesar's code , or Caesar shift , is one of the simplest and most widely known encryption techniques.