How to implement SM3 algorithm in PHP

The SM3 algorithm is a cryptographic hash function algorithm launched by the China Computer Cryptography Research Center in 2010. It is known as a very important algorithm in national secrets. In this article, we will introduce how to implement the SM3 algorithm in PHP.

1. Introduction to the algorithm

SM3 algorithm is a cryptographic hash function algorithm. A cryptographic hash function accepts data of any size as input and converts it into a fixed-length output, and the output value is different for different input values. The password hash function has the following characteristics:

1. Fixed length: The output length of the password hash function should be fixed, usually 128, 160, 192, 224 or 256 bits.

2. Irreversibility: Given a hash output, its input cannot be determined, which is called a one-way hash function.

3. Strong resistance: Given a hash value, it is impossible to find any input with the same hash value, while changing only a single or limited number of bits in the input means producing a different input than the original output.

The SM3 algorithm uses the Merkle-Damgard structure to split the message into blocks and perform iterative compression processing.

Algorithm processing is divided into 4 parts:

1. Padding: Pad the message to ensure that its length is a multiple of 512 bits.

2. Compression: Process blocks into 256-bit message digests.

3. Iteration: Process each message block iteratively until all blocks are compressed.

4. Output: Generate the final 256-bit digest.

2. PHP implementation

1. Padding

Implement the padding function in PHP to ensure that the message length is a multiple of 512 bits.

function padding($msg) {

$length = strlen($msg) * 8;  // 消息长度，单位是比特
$k = 448 - (($length + 64) % 512);  // 填充长度
if ($k < 0) {
    $k += 512;
}
$msg .= hex2bin("80");  // 消息后面添加1
for ($i = 0; $i < $k / 8 - 1; $i++) {
    $msg .= hex2bin("00");  // 用0填充
}
$msg .= pack("N", $length);  // 添加消息长度
return $msg;

}

2. Compression

Implement the compression function in PHP to process 512-bit message blocks A 256-bit message digest.

function CF($X, $Y, $Z) {

return ($X & $Y) | (~$X & $Z);

}
function MG($X, $Y, $Z) {

return ($X & $Y) | ($X & $Z) | ($Y & $Z);

}
function P0($X) {

return $X ^ (($X << 9) | ($X >> 23)) ^ (($X << 17) | ($X >> 15));

}
function P1($X) {

return $X ^ (($X << 15) | ($X >> 17)) ^ (($X << 23) | ($X >> 9));

}
function FF($X, $Y, $ Z, $j) {

if ($j >= 0 && $j <= 15) {
    return P0($X ^ $Y ^ $Z);
} else {
    return P1($X ^ $Y ^ $Z);
}

}
function GG($X, $Y, $Z, $j) {

if ($j >= 0 && $j <= 15) {
    return P0($X ^ $Y ^ $Z);
} else {
    return P1($X ^ $Y ^ $Z);
}

}
function SM3_compress($msg, $IV) {

$W = array();
$V = $IV;
$A = $IV[0];
$B = $IV[1];
$C = $IV[2];
$D = $IV[3];
$E = $IV[4];
$F = $IV[5];
$G = $IV[6];
$H = $IV[7];
for ($i = 0; $i < 16; $i++) {
    $W[$i] = unpack("N", substr($msg, $i * 4, 4))[1];
}
for ($j = 16; $j < 68; $j++) {
    $W[$j] = GG($W[$j - 16] ^ $W[$j - 9] ^ ($W[$j - 3] << 15) ^ ($W[$j - 13] >> 17), 15) ^ ($W[$j - 6] << 7) ^ $W[$j - 16];
}
for ($j = 0; $j < 64; $j++) {
    $SS1 = ($A << 12) | ($A >> 20);
    $SS2 = ($SS1 << 7) | ($SS1 >> 25);
    $TT1 = FF($A, $B, $C, $j) + $D + $SS2 + $W[$j] + (0x79cc4519 >> $j);
    $SS1 = ($E << 12) | ($E >> 20);
    $SS2 = ($SS1 << 7) | ($SS1 >> 25);
    $TT2 = GG($E, $F, $G, $j) + $H + $SS2 + $W[$j] + (0x7a879d8a >> $j);
    $D = $C;
    $C = ($B << 9) | ($B >> 23);
    $B = $A;
    $A = $TT1;
    $H = $G;
    $G = ($F << 19) | ($F >> 13);
    $F = $E;
    $E = P0($TT2);
}
$V[0] = $V[0] ^ $A;
$V[1] = $V[1] ^ $B;
$V[2] = $V[2] ^ $C;
$V[3] = $V[3] ^ $D;
$V[4] = $V[4] ^ $E;
$V[5] = $V[5] ^ $F;
$V[6] = $V[6] ^ $G;
$V[7] = $V[7] ^ $H;
return $V;

}

3. Iteration

Implement the iteration function in PHP and process each message block iteratively until all blocks are compressed.

function SM3($msg) {

$IV = array(
    0x7380166f, 0x4914b2b9, 0x172442d7, 0xda8a0600,
    0xa96f30bc, 0x163138aa, 0xe38dee4d, 0xb0fb0e4e
);
$msg = padding($msg);
$n = strlen($msg) / 64;
for ($i = 0; $i < $n; $i++) {
    $block = substr($msg, $i * 64, 64);
    $IV = SM3_compress($block, $IV);
}
$digest = "";
foreach ($IV as $v) {
    $digest .= str_pad(dechex($v), 8, "0", STR_PAD_LEFT);
}
return $digest;

}

4. Algorithm testing

In order to verify whether our implementation is correct, we can use GM/ T 0004-2012 Cryptographic Hash Algorithm Test.

require_once "sm3.php";
$input = "abc";
$expected_output = "66C7F0FAD8E2DDDB2D0A6EEA2E2ECEB4E83441BEC4C3056BFCDC6F7E9
D9E8B7F5D6A5B96D011A7B 19A1456";

$output = SM3($input);
var_dump($output === $expected_output); // true
?>

We can also use other messages to test and verify our Is the implementation correct?

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