Static Public Member Functions
static	generate ( $bytes, $context)
	Generate cryptographically random data and return it in raw binary form. More...

static	generateHex ( $chars, $context='')
	Generate cryptographically random data and return it in hexadecimal string format. More...

static	HKDF ( $hash, $ikm, $salt, $info, $L)
	RFC5869 defines HKDF in 2 steps, extraction and expansion. More...

Static Protected Member Functions
static	singleton ()
	Return a singleton instance, based on the global configs. More...

Detailed Description

Definition at line 35 of file MWCryptHKDF.php.

Member Function Documentation

◆ generate()

static MWCryptHKDF::generate	(	$bytes,
		$context
	)

static

Generate cryptographically random data and return it in raw binary form.

Parameters

int	$bytes	The number of bytes of random data to generate
string	$context	String to mix into HMAC context

Returns: string Binary string of length $bytes

Definition at line 85 of file MWCryptHKDF.php.

References $context, and singleton().

Referenced by generateHex().

◆ generateHex()

static MWCryptHKDF::generateHex	(	$chars,
		$context = `''`
	)

static

Generate cryptographically random data and return it in hexadecimal string format.

See MWCryptRand::realGenerateHex for details of the char-to-byte conversion logic.

Parameters

int	$chars	The number of hex chars of random data to generate
string	$context	String to mix into HMAC context

Returns: string Random hex characters, $chars long

Definition at line 97 of file MWCryptHKDF.php.

References $context, and generate().

Referenced by MWCryptHKDFTest\testGenerate().

◆ HKDF()

static MWCryptHKDF::HKDF	(	$hash,
		$ikm,
		$salt,
		$info,
		$L
	)

static

RFC5869 defines HKDF in 2 steps, extraction and expansion.

From http://eprint.iacr.org/2010/264.pdf:

The scheme HKDF is specifed as: HKDF(XTS, SKM, CTXinfo, L) = K(1) || K(2) || ... || K(t) where the values K(i) are defined as follows: PRK = HMAC(XTS, SKM) K(1) = HMAC(PRK, CTXinfo || 0); K(i+1) = HMAC(PRK, K(i) || CTXinfo || i), 1 <= i < t; where t = [L/k] and the value K(t) is truncated to its first d = L mod k bits; the counter i is non-wrapping and of a given fixed size, e.g., a single byte. Note that the length of the HMAC output is the same as its key length and therefore the scheme is well defined.

XTS is the "extractor salt" SKM is the "secret keying material"

N.B. http://eprint.iacr.org/2010/264.pdf seems to differ from RFC 5869 in that the test vectors from RFC 5869 only work if K(0) = '' and K(1) = HMAC(PRK, K(0) || CTXinfo || 1)

Parameters

string	$hash	The hashing function to use (e.g., sha256)
string	$ikm	The input keying material
string	$salt	The salt to add to the ikm, to get the prk
string	$info	Optional context (change the output without affecting the randomness properties of the output)
int	$L	Number of bytes to return