jsrsasign

The jsrsasign-util package provides supplementary functions for the main jsrsasign library, specifically focusing on file I/O utilities like reading and saving files in various formats (binary, hex, UTF-8).

var rsu = require('jsrsasign-util');

To use the sample Node.js utility scripts provided in this repository, you must install the following npm packages globally. Since version 6.0.0, logic involving the fs module has been moved to jsrsasign-util, making it a required dependency alongside jsrsasign and commander.

% npm install -g commander
% npm install -g jsrsasign
% npm install -g jsrsasign-util

You can install jsrsasign using npm, Bower, or by including it directly in an HTML file via a CDN.

# Node NPM
npm install jsrsasign jsrsasign-util

# Bower
bower install jsrsasign

To use the library in a browser environment without a package manager, include the minified script from a CDN.

<script src="https://cdnjs.cloudflare.com/ajax/libs/jsrsasign/8.0.20/jsrsasign-all-min.js"></script>

End of Support

As of 14 April 2026, support for jsrsasign has ended. Effective 3 June 2026, all npm packages for jsrsasign are deprecated.

Security Advisory: Marvin Attack

Due to the Marvin attack vulnerability (CVE-2024-21484), RSA PKCS#1.5 and RSAOAEP encryption/decryption are no longer supported in version 11.0.0 and later.

The asn1dump script provides a simple way to dump the contents of an ASN.1 DER formatted binary file into a readable format.

% asn1dump aaa.pub.p8.der

This example demonstrates how to require the utility module, read a binary file, and save a file from a hexadecimal string.

var rsu = require('jsrsasign-util');
var rawString = rsu.readFile("bar.bin");
rsu.saveFileBinByHex("foo.bin", "30143abb...");

The pemtobin script converts any PEM format file into its binary representation.

% pemtobin aaa.pem aaa.der

To load an encrypted PKCS#5 private key, use jsrsasign-util to read the file and jsrsasign.KEYUTIL.getKey to parse it with the provided password.

var rs = require('jsrsasign');
var rsu = require('jsrsasign-util');
var pem = rsu.readFile('z1.prv.p5e.pem');
var prvKey = rs.KEYUTIL.getKey(pem, 'passwd');

To sign a string using a loaded private key, instantiate a Signature object with the desired algorithm (e.g., 'SHA1withRSA'), initialize it with the private key, update it with the string content, and call .sign().

var sig = new Signature({alg: 'SHA1withRSA'});
sig.init(prvKey);
sig.updateString('aaa');
var sigVal = sig.sign();
// sigVal contains the signature