hash

type Hash interface {
	// Write (via the embedded io.Writer interface) adds more data to the running hash.
	// It never returns an error.
	io.Writer

	// Sum appends the current hash to b and returns the resulting slice.
	// It does not change the underlying hash state.
	Sum(b []byte) []byte

	// Reset resets the Hash to its initial state.
	Reset()

	// OutputSize returns the number of bytes Sum will return.
	OutputSize() int

	// BlockSize returns the hash's underlying block size.
	// The Write method must be able to accept any amount
	// of data, but it may operate more efficiently if all writes
	// are a multiple of the block size.
	BlockSize() int

	// MustWriteAll writes all inputs into the hash's state.
	MustWriteAll(inputs ...[]byte) error

	// MustReadFull reads exactly len(buf) bytes from hash's state.
	// It does not change the underlying hash state.
	MustReadFull(buff []byte) error

	// String returns string representation of the hash algorithm.
	String() string

	// Hmac wraps the built-in hmac.
	Hmac(message, key []byte) ([]byte, error)

	// HKDFExtract is an "extract" only HKDF, where the secret and salt are used to generate a pseudorandom key. This key
	// can then be used in multiple HKDFExpand calls to derive individual different keys.
	HKDFExtract(secret, salt []byte) []byte

	// HKDFExpand is an "expand" only HKDF, where the key should be an already random/hashed input,
	// and info specific key usage identifying information.
	HKDFExpand(pseudorandomKey, info []byte, length int) []byte
}

type Hashing uint