go-dedis-kyber/docs/xof.md

Introduction

An XOF is an extendable output function, which is a cryptographic primitive that can take arbitrary input in the same way a hash function does, and then create a stream of output, up to a limit determined by the size of the internal state of the hash function the underlies the XOF.

When XORKeyStream is called with zeros for the source, an XOF also acts as a PRNG. If it is seeded with an appropriate amount of keying material, it is a cryptographically secure source of random bits.

type XOF interface {
	io.Writer
	io.Reader
	cipher.Stream

	Reseed()
	Clone() XOF
}

Members

Writer

The XOF interface consists of an io.Writer. The Write function of Writer absorbs more data into the hash's state. It panics if called after Read function of the io.Reader interface. Use Reseed() to reset the XOF into a state where more data can be absorbed via Write.

Reader

The Read function of the io.Reader interface reads more output from the hash. It returns io.EOF if the limit of available data for reading has been reached.

Stream

An XOF implements cipher.Stream, so that callers can use XORKeyStream to encrypt/decrypt data. The key stream is read from the XOF using the io.Reader interface. If Read returns an error, then XORKeyStream will panic.

Functions

Reseed()

The Reseed function makes the caller XOF writeable again after it has been read from by sampling a key from it's output and initializing a fresh XOF implementation with that key.

Function	XOF.Reseed()
Parameters	- None
Output	- None

Clone()

Clone returns a copy of the caller XOF in its current state.

Function	XOF.Clone() XOF
Parameters	- None
Output	- XOF : A new XOF which is a clone of the caller XOF