I am consuming a java web service in Apex that needs a security hash computed using MD5 or SHA1, and the digest produced by the Crypto class is not matching the output of the Java algorithm for either method. Here is the Apex code, which I have broken up into several lines in order to print interim debug information:

public static String createHash(String preHashValue) {

System.debug('Prehashvalue: ' + preHashValue);

Blob bPrehash = Blob.valueOf(preHashValue);

System.debug('\n----Blob.valueOf(preHashValue): ' + bPrehash.toString());

String convertedPrehash = EncodingUtil.convertToHex(bPrehash);

System.debug('\nHex prehash value: ' + convertedPrehash);

Blob bHexPrehash = Blob.valueOf(convertedPrehash);

System.debug('\nBlob.valueOf(convertedPrehash): ' + bHexPrehash.toString());

Blob bsig = Crypto.generateDigest('SHA1', bHexPrehash);

System.debug('\n--------Blob version of digest: ' + bsig.toString());

String result = EncodingUtil.convertToHex(bsig);

System.debug('\n--------------Hex digest value: ' + result);

return result;

}

And the corresponding Java code:

private static String CreateHash(String preHashVal) {

java.security.MessageDigest algorithm;

String md5val = null;

try {

// algorithm = java.security.MessageDigest.getInstance("MD5");

algorithm = java.security.MessageDigest.getInstance("SHA1");

byte[] defaultBytes = preHashVal.getBytes();

System.out.println("Prehash value as bytes: '" + bytesToHexString(defaultBytes) + "'");

algorithm.reset();

algorithm.update(defaultBytes);

byte[] messageDigest = algorithm.digest();

System.out.println("Computed digest: '" + bytesToHexString(messageDigest) + "'");

StringBuffer hexString = new StringBuffer();

for (int i = 0; i < messageDigest.length; i++) {

String hex = Integer.toHexString(0xFF & messageDigest[i]);

if (hex.length() == 1) {

hexString.append('0');

}

hexString.append(hex);

}

md5val = hexString.toString();

} catch (Exception e) {

e.printStackTrace();

}

return md5val;

}

Using the same "prehashvalue", which is just a constant, a secret code and a random number, they produce the same values in the log output until Crypto.generateDigest('SHA1', bHexPrehash)  and algorithm.digest().

Since neither of these methods has a lot of flexibility in terms of options, I have no idea how to get the hash to work out on both sides. Also, the Java side is code I do not control. I would be truly obligated for your help if you can spot where I have made a mistake.

--k