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Symmetric-key encryption: the same key is used for both encryption and decryption. 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]
56-bit refers to the size of a symmetric key used to encrypt data, with the number of unique possible permutations being (72,057,594,037,927,936). 56-bit encryption has its roots in DES , which was the official standard of the US National Bureau of Standards from 1976, and later also the RC5 algorithm.
The Data Encryption Standard (DES / ˌ d iː ˌ iː ˈ ɛ s, d ɛ z /) is a symmetric-key algorithm for the encryption of digital data. Although its short key length of 56 bits makes it too insecure for modern applications, it has been highly influential in the advancement of cryptography .
In symmetric-key schemes, [12] the encryption and decryption keys are the same. Communicating parties must have the same key in order to achieve secure communication. The German Enigma Machine used a new symmetric-key each day for encoding and decoding messages.
In cryptography, key size or key length refers to the number of bits in a key used by a cryptographic algorithm (such as a cipher).. Key length defines the upper-bound on an algorithm's security (i.e. a logarithmic measure of the fastest known attack against an algorithm), because the security of all algorithms can be violated by brute-force attacks.
KeyExpansion – round keys are derived from the cipher key using the AES key schedule. AES requires a separate 128-bit round key block for each round plus one more. Initial round key addition: AddRoundKey – each byte of the state is combined with a byte of the round key using bitwise xor. 9, 11 or 13 rounds:
Public/private key pairs used in asymmetric encryption (public key cryptography), at least those based on prime factorization, must be much longer in order to be secure; see key size for more details. As a general rule, modern symmetric encryption algorithms such as AES use key lengths of 128, 192 and 256 bits.
Mathematically, a cryptosystem or encryption scheme can be defined as a tuple (,,,,) with the following properties.. is a set called the "plaintext space". Its elements are called plaintexts.; is a set called the "ciphertext space". Its elements are called ciphertexts.; is a set called the "key space". Its elements are called keys.; = {:} is a set of functions :. Its elements are called ...