PHP doing a SHA256 hash signature on a string - php

Question

I am trying to sign a string with the secret key I have, but it keeps failing. I am new to this and are just starting to understand it a little bit (encryption and base64). But I have been stuck at this point for three days now and have pulled out all of my hairs. I just dont get it.
The bit from the api is:
MD5 Digest
MD5 algorithm is used to perform a signature operation on the final string to be signed, thereby obtaining a signature hex result string (this string is assigned to the parameter sign). In the MD5 calculation result, letters are all capitalized.
RSA Signature
Users could use their private key to perform a signature operation (Base64 coded) to a MD5 digest by implementing SHA256 algorithm through RSA, after users getting the signature result string which is signed by MD5 algorithm.
All I have tried:
$echostr="SS...AD";
$api_key="17...e0";
$secret="EB....D";
$parameters="api_key=".$api_key."&echostr=".$echostr."&signature_method=HmacSHA256&timestamp=".$timeStamp;
$preparedStr=base64_encode(strtoupper(md5($parameters)));
$sign=rsa_hash_sign($preparedStr, $secret);
echo "1 ".$sign."<\br>";
$sign=HmacSHA256_Sign($preparedStr, $secret);
echo "2 ".$sign."<\br>";
$sign=GenerateDigest($secret);
echo "3 ".$sign."<\br>";
$binaryKey = decode($secret);
$sign=encode(hash_hmac("sha256", $preparedStr, $binaryKey, true));
echo "4 ".$sign."<\br>";
$sign=hash_hmac("sha256", $preparedStr, $binaryKey, true);
echo "5 ".$sign."<\br>";
$sign=base64_encode(hash_hmac('sha256', base64_encode($preparedStr), $secret,true));
echo "6 ".$sign."<br>";
$cURLConnection = curl_init('...');
curl_setopt($cURLConnection, CURLOPT_POSTFIELDS, array(
'sign' => $sign,
'api_key' => $api_key
));
curl_setopt($cURLConnection, CURLOPT_HTTPHEADER, array(
'contentType: application/x-www-form-urlencoded',
'timestamp: '.$timeStamp,
'signature_method: HmacSHA256',//RSA
'echostr: '.$echostr
));
curl_setopt($cURLConnection, CURLOPT_RETURNTRANSFER, true);
$apiResponse = curl_exec($cURLConnection);
curl_close($cURLConnection);
var_dump($apiResponse);
function encode($data) {
return str_replace(['+', '/'], ['-', '_'], base64_encode($data));
}
function decode($data) {
return base64_decode(str_replace(['-', '_'], ['+', '/'], $data));
}
function GenerateDigest($requestPayload)
{
$utf8EncodedString = utf8_encode($requestPayload);
$digestEncode = hash("sha256", $utf8EncodedString, true);
return base64_encode($digestEncode);
}
function rsa_hash_sign($package, $privateKey) {
$rsa = new Crypt_RSA();
$rsa->setHash("sha256");
$rsa->setSignatureMode(CRYPT_RSA_SIGNATURE_PKCS1);
$rsa->loadKey($privateKey);
$hash = hash('sha256', $package, true);
$signature = $rsa->sign($hash);
$hexData = bin2hex($signature);
$base64 = base64_encode($hexData);
return $base64;
}
function HmacSHA256_Sign($preparedStr, $secret)
{
signature result string which is signed by MD5 algorithm.
$hash = "";
$rsa = new Crypt_RSA();
$rsa->setHash('sha256');
$rsa->setSignatureMode(CRYPT_RSA_SIGNATURE_PKCS1);
$rsa->loadKey($secret);
return $rsa->encrypt($secret);
}
But every $sign I try is giving me "Secret key does not exist" back as error. This is my first time trying anything with encryption and I am so lost and dont know how to solve this.