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Cryptography. Cryptography, or cryptology (from Ancient Greek: κρυπτός, romanized : kryptós "hidden, secret"; and γράφειν graphein, "to write", or -λογία -logia, "study", respectively [ 1] ), is the practice and study of techniques for secure communication in the presence of adversarial behavior. [ 2]
Frequency analysis relies on a cipher failing to hide these statistics. For example, in a simple substitution cipher (where each letter is simply replaced with another), the most frequent letter in the ciphertext would be a likely candidate for "E". Frequency analysis of such a cipher is therefore relatively easy, provided that the ciphertext ...
A disk cipher device of the Jefferson type from the 2nd quarter of the 19th century in the National Cryptologic Museum. The Jefferson disk, also called the Bazeries cylinder or wheel cypher, [1] was a cipher system commonly attributed to Thomas Jefferson that uses a set of wheels or disks, each with letters of the alphabet arranged around their edge in an order, which is different for each ...
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.
Bacon's cipher or the Baconian cipher is a method of steganographic message encoding devised by Francis Bacon in 1605. [ 1][ 2][ 3] A message is concealed in the presentation of text, rather than its content. Baconian ciphers are categorized as both a substitution cipher (in plain code) and a concealment cipher (using the two typefaces).
The level of expense required for strong cryptography originally restricted its use to the government and military agencies, [9] until the middle of the 20th century the process of encryption required a lot of human labor and errors (preventing the decryption) were very common, so only a small share of written information could have been encrypted. [10]
Lattice-based cryptography is the generic term for constructions of cryptographic primitives that involve lattices, either in the construction itself or in the security proof. Lattice-based constructions support important standards of post-quantum cryptography. [ 1] Unlike more widely used and known public-key schemes such as the RSA, Diffie ...
Symmetric-key algorithms[ a] are algorithms for cryptography that use the same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext. The keys may be identical, or there may be a simple transformation to go between the two keys. [ 1] The keys, in practice, represent a shared secret between two or more parties ...