In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called blocks, with an unvarying transformation that is specified by a symmetric key.

* By whether the same key is used for both encryption and decryption ( symmetric key algorithms ), or if a different key is used for each ( asymmetric key algorithms ).

If the algorithm is symmetric, the key must be known to the recipient and sender and to no one else.

* symmetric key algorithms ( Private-key cryptography ), where the same key is used for encryption and decryption, and

In a symmetric key algorithm ( e. g., DES and AES ), the sender and receiver must have a shared key set up in advance and kept secret from all other parties ; the sender uses this key for encryption, and the receiver uses the same key for decryption.

For example, the security available with a 1024-bit key using asymmetric RSA is considered approximately equal in security to an 80-bit key in a symmetric algorithm ( Source: RSA Security ).

Since longer symmetric keys require exponentially more work to brute force search, a sufficiently long symmetric key makes this line of attack impractical.

Moore's law suggests that computing power doubles roughly every 18 to 24 months, but even this doubling effect leaves the larger symmetric key lengths currently considered acceptable well out of reach.

NIST key management guidelines further suggest that 15360-bit RSA keys are equivalent in strength to 256-bit symmetric keys.

NIST guidelines state that ECC keys should be twice the length of equivalent strength symmetric key algorithms.

So, for example, a 224-bit ECC key would have roughly the same strength as a 112-bit symmetric key.

This implies that at least a 160-bit symmetric key is required to achieve 80-bit security rating against a quantum computer.

This key can then be used to encrypt subsequent communications using a symmetric key cipher.

" An astonishing share of the open literature in cryptography in the 1970s and 1980s dealt with the DES, and the DES is the standard against which every symmetric key algorithm since has been compared.

Common families include symmetric systems ( e. g. AES ) and asymmetric systems ( e. g. RSA ); they may alternatively be grouped according to the central algorithm used ( e. g. elliptic curve cryptography ).

In cryptography, a stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream ( keystream ).

Secret-key ( symmetric ) cryptography requires the initial exchange of a shared key in a manner that is private and integrity-assured.

In cryptography, RC6 is a symmetric key block cipher derived from RC5.

Random numbers are used in both symmetric and asymmetric cryptography as a way of generating keys and for the random values used in the operation of some algorithms.

* Private-key cryptography ( symmetric key algorithm ): the same key is used for encryption and decryption

TLS and SSL encrypt the segments of network connections at the Application Layer for the Transport Layer, using asymmetric cryptography for key exchange, symmetric encryption for confidentiality, and message authentication codes for message integrity.

In cryptography, an S-Box ( Substitution-box ) is a basic component of symmetric key algorithms which performs substitution.

In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers.

This requirement of on-line validation negates one of the original major advantages of PKI over symmetric cryptography protocols, namely that the certificate is " self-authenticating ".

In cryptography, a Feistel cipher is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel who did pioneering research while working for IBM ( USA ); it is also commonly known as a Feistel network.

The payment system utilized symmetric cryptography.

In traditional symmetric key cryptography, this problem wasn't an issue as it was implicitly assumed that some " secure " method of key distribution guaranteed key authenticity.

Higher-layer processes may specify keys to perform symmetric cryptography to protect the payload and restrict it to a group of devices or just a point-to-point link ; these groups of devices can be specified in access control lists.

It has an entity authentication mechanism, based on the X. 509 system ; a key setup phase, where a symmetric encryption key is formed by employing public-key cryptography ; and an application-level data transport function.

In cryptography, MAGENTA is a symmetric key block cipher developed by Michael Jacobson Jr. and Klaus Huber for Deutsche Telekom.

In the Microsoft Windows family of operating systems EFS enables this measure, although on NTFS drives only, and does so using a combination of public key cryptography and symmetric key cryptography to make decrypting the files extremely difficult without the correct key.

* In cryptography, sinople is a 128-bit symmetric block cipher

In cryptography, NewDES is a symmetric key block cipher.

Part of the role of the SSL handshake is to agree on session keys ( symmetric keys, used for the duration of a given session ), but the encryption and signature of the SSL handshake messages itself is done using asymmetric keys ( contained in the certificates ), which requires more computational power than the symmetric cryptography used for the encryption / decryption of the session data.

A relation can be both symmetric and antisymmetric ( e. g., the equality relation ), and there are relations which are neither symmetric nor antisymmetric ( e. g., the " preys on " relation on biological species ).

In both animations the function g is symmetric, and so is unchanged under reflection.

There may also be symmetric flow from both loop foot points, causing a buildup of mass in the loop structure.

The Ctenophora and the Cnidaria, which includes sea anemones, corals, and jellyfish, are radially symmetric and have digestive chambers with a single opening, which serves as both the mouth and the anus.

Multiplying both sides of this equation by ( x < sub > 2 </ sub > − x < sub > 1 </ sub >) yields a form of the line generally referred to as the symmetric form:

If they did exist, both Gauss's law for magnetism and Faraday's law would need to be modified, and the resulting four equations would be fully symmetric under the interchange of electric and magnetic fields ; see magnetic monopoles for details.

A zero value indicates that the values are relatively evenly distributed on both sides of the mean, typically but not necessarily implying a symmetric distribution.

Assuming both sidebands are symmetric, which is the case for a normal AM signal, no information is lost in the process.

This is true for both asymmetric and symmetric TSPs ( Gutin and Yeo, 2007 ).

Encryption algorithms which use the same key for both encryption and decryption are known as symmetric key algorithms.

This requirement that both parties have access to the secret key is one of the main drawbacks of symmetric key encryption, in comparison to public-key encryption.

Arginine can be methylated once ( monomethylated arginine ) or twice, with either both methyl groups on one terminal nitrogen ( asymmetric dimethylated arginine ) or one on both nitrogens ( symmetric dimethylated arginine ) by peptidylarginine methyltransferases ( PRMTs ).

A Jacobi rotation has the same form as a Givens rotation, but is used to zero both off-diagonal entries of a 2 × 2 symmetric submatrix.

If A and B are n × n real symmetric matrices that commute, then there exists a basis of such that every element of the basis is an eigenvector for both A and B.

Objects that have the same shape or one has the same shape as the other's mirror image ( or both if they are themselves symmetric ) are called geometrically similar.

In both of these, initial set-up of a secure channel ( a " security association ") uses asymmetric key ( a. k. a. public-key ) methods, whereas actual communication uses faster symmetric key ( a. k. a. secret key ) methods.

A character such as " H " fits the definition of both symmetric and antisymmetric.

There are relations which are both symmetric and antisymmetric ( equality and its subrelations, including, vacuously, the empty relation ), there are relations which are neither symmetric nor antisymmetric ( the relation " divides " on the set ℤ ; the relation " preys on " in biological sciences ), there are relations which are symmetric and not antisymmetric ( congruence modulo n ), and there are relations which are not symmetric but are antisymmetric (" is less than or equal to ").