How deeply does Real-World Cryptography cover extendable output function?

Defines SHAKE and cSHAKE, explains squeezing and customization, and stops short of detailed construction internals.

Extendable output function

An extendable output function is a cryptographic function that maps an input to an output of a caller-selected length.

An extendable output function maps an arbitrary-length input to a caller-selected output length. Unlike a fixed-digest hash, it can produce exactly as many output bytes as a protocol needs. section 2.5.3

Two standardized choices cover the main use cases:

SHAKE works like SHA-3 but continues its squeezing phase to produce outputs of arbitrary length, supporting digests, random numbers, and key derivation. section 2.5.3
cSHAKE adds a customization string, producing distinct deterministic outputs for different contexts and enabling domain separation. section 2.5.3

Customize the same input

cSHAKE("hello world", 256, "my_hash") and cSHAKE("hello world", 256, "your_hash") produce different digests because their customization strings differ.

How Real-World Cryptography covers it

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Related concepts

cSHAKEincludes · cSHAKE is a customizable extendable output function in the SHA-3 family that accepts a function-name string and an optional customization string.
cryptographic primitivekind of · A cryptographic primitive is a fundamental algorithmic building block that provides a basic security function such as encryption, hashing, or digital signing.
hash functioncontrasts with · A hash function deterministically maps input data to a value in a bounded output range, commonly for indexing, lookup, comparison, or integrity checking.
key derivation functionalternative to · A key derivation function transforms input keying material into one or more cryptographic keys or related pseudorandom values.

This explainer was generated by Manning's knowledge graph from the text of Real-World Cryptography. The section links point to the parts of the book it draws on.