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Example of a Key Derivation Function chain as used in the Signal Protocol.The output of one KDF function is the input to the next KDF function in the chain. In cryptography, a key derivation function (KDF) is a cryptographic algorithm that derives one or more secret keys from a secret value such as a master key, a password, or a passphrase using a pseudorandom function (which typically uses a ...
In cryptography, a shared secret is a piece of data, known only to the parties involved, in a secure communication. This usually refers to the key of a symmetric cryptosystem . The shared secret can be a PIN code , a password , a passphrase , a big number, or an array of randomly chosen bytes.
Elliptic-curve Diffie–Hellman (ECDH) is a key agreement protocol that allows two parties, each having an elliptic-curve public–private key pair, to establish a shared secret over an insecure channel. [1] [2] [3] This shared secret may be directly used as a key, or to derive another key.
Some ciphers have simple key schedules. For example, the block cipher TEA splits the 128-bit key into four 32-bit pieces and uses them repeatedly in successive rounds.; DES has a key schedule in which the 56-bit key is divided into two 28-bit halves; each half is thereafter treated separately.
The shared secret can be used, for instance, as the key for a symmetric cipher. If the sender and receiver wish to exchange encrypted messages, each must be equipped to encrypt messages to be sent and decrypt messages received. The nature of the equipping they require depends on the encryption technique they might use. If they use a code, both ...
This design makes it easy to reuse Ascon in multiple ways (as a cipher, hash, or a MAC). [4] As of February 2023, the Ascon suite contained seven ciphers, [3] including: [5] Ascon-128 and Ascon-128a authenticated ciphers; Ascon-Hash cryptographic hash; Ascon-Xof extendable-output function; Ascon-80pq cipher with an "increased" 160-bit key.
The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information link. [2] The 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 (also known as asymmetric-key encryption).
This was the first published practical method for establishing a shared secret-key over an authenticated (but not confidential) communications channel without using a prior shared secret. Merkle's "public key-agreement technique" became known as Merkle's Puzzles, and was invented in 1974 and only published in 1978. This makes asymmetric ...