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How to create a checksum hash in JavaScript, maybe MD5?

medini_1023641097

Hi,

does anyone know an efficient way to create checksum in JavaScript?

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medini_1024169437

Hi Nino,

at first I thought that should be either feasible with some JS script out there or - if not available - definitely with some Java library offered by medini. Then I read about JSum in this article and recognized that JSum is partially right: for normal hashes it matters whether you have a data before the other one, for JSON it might not be right because semantically { a:'foo':, b:'bar' } is the same as { b:'bar', a:'foo': }.

Anyway, I did not try to get JSUm running in medini scripting. All I can offer is a straight way to directly use internal Java classes to generate an MD5 (or other) hash, look at this:

var text1 = '.....';
var text2 = '.....';
var md = java.security.MessageDigest.getInstance('MD5');
md.update(text1.getBytes("UTF8"));
md.update(text2.getBytes("UTF8"));
...
var lastHash = md.digest();
var prettyHash = javax.xml.bind.DatatypeConverter.printHexBinary(lastHash).toLowerCase();

I hope that this gives you, and anyone else having the same or similar question a start.

Happy Scripting

Jan

medini_1023641097

Thank you Jan,

unfortunately I do not understand the solution

By reading the article I understand that the author caters to a very specific issue which is order of elements in a Java object. I don't have that issue, my objects are well formed.

I now use this snipped that I found in an otherwise empty drawer, it works a treat

function checksum(s)
{
 var chk = 0x12345678;
 var len = s.length;
 for (var i = 0; i < len; i++) {
 chk += (s.charCodeAt(i) * (i + 1));
 }

 return (chk & 0xffffffff).toString(16);
}

medini_1024169437

Nice, I assume s is an array, I was rather referring to a Java Script object.

Anyway, glad you found this solution.

Jan

medini_1023641097

s is actually a string here, I now edited the above post and changed the variable "s" to "text" to make it more obvious

medini_1052680584

Hi Jan,

Do you have a full snippet for generating MD5 (or SHA256 for that matter) of a string using the java libraries? (Nino's solution above apparently is unique for small strings only).

Somewhat I am not able to adapt your code above using java libraries... for example it does not seem to understand the getBytes method, so maybe I have to import/load something before (?)

Thanks for any help!

Cheers, Andre

medini_1024169437

Andre,

my bad. The getBytes() method is part of the java.lang.String API, not the JS string.

The MessageDigest accepts only BLOBs, so byte[]. We either have to find a way to convert a JS string to bytes (there are some articles arround) or you have to convert a JS string to a Java String first:

var javaString = new java.lang.String('foo bar');

var bytes = javaString.getBytes(...)

Maybe you can take it from here.

Regards

Jan

medini_1052680584

Hi Jan,

Thanks a lot! Now it works. I put the snippet below for completeness.

Cheers, Andre

	// create md5 instance
	var md = java.security.MessageDigest.getInstance('MD5');
	// string to be hashed
	var myJSString = 'Liberté, Egalité, Fraternité';
	var javaString = new java.lang.String(myJSString);
	//actual hashing
	md.update(javaString.getBytes("UTF8"));
	var lastHash = md.digest();
	var prettyHash = javax.xml.bind.DatatypeConverter.printHexBinary(lastHash).toLowerCase();
	//result should be: 9f232781d916abd12f528fba71dbacb7
	console.log(prettyHash);

medini_1024169437

Nice, I like 'Liberté, Egalité, Fraternité' :-)

If you agree, I could add this to the helper.js so everyone has it for the future-

Jan

medini_1052680584

Sure!

medini_1052680584

Hi Jan,

I only tested successfully the code above in the v2020R2 version. When I tried it this morning

in the v2023R1.1, I get the error below. Any ideas of why is that happening?

Thanks for any help!

Regards, Andre

medini_1024169437

Not 100% sure but javax.xml may has changed when we moved to Java 11. We may have to find another way to pretty print the hash value.

Jan

medini_1024169437

Andre, it might be that the javax.xml package is simply not anymore in the standard classpath and you have to use "bind" to load it from the "javax.xml.bind" bundle.

I did not find the time to prove this though.

Jan

medini_1024169437

Andre,

this worked for me as expected:

var DatatypeConverter = bind("javax.xml.bind", "javax.xml.bind.DatatypeConverter", false);
....
var prettyHash = DatatypeConverter.printHexBinary(lastHash).toLowerCase();

medini_1052680584

Hi Jan,

Thanks for the feedback on the bind approach. I've found another solution as well so I put them as alternatives in the snippet below. Both are working on v2020 and v2023.

Regards, Andre

	// create md5 instance
	var md = java.security.MessageDigest.getInstance('MD5');
	// string to be hashed
	var myJSString = 'Liberté, Egalité, Fraternité';
	var javaString = new java.lang.String(myJSString);
	//actual hashing
	md.update(javaString.getBytes("UTF8"));
	var lastHash = md.digest();

	//	option 1 (comment option 2)
	var prettyHash = new java.lang.String.format("%032x", new java.math.BigInteger(1, lastHash));

	//	option 2 (comment option 1)	
//	var DatatypeConverter = bind("javax.xml.bind", "javax.xml.bind.DatatypeConverter", false);
//	var prettyHash = DatatypeConverter.printHexBinary(lastHash).toLowerCase();

	// output should be 9f232781d916abd12f528fba71dbacb7
	console.log(prettyHash);

medini_1024169437

Very cool Andre,

that solution is even smarter because it doe snot introduce another dependency, well done.

I found an (the?) article on stackoverflow and that solution was not (yet?) the one with the highest votes as it is rather new.

Cool stuff

Jan