RSA and ECC in JavaScript

Demos

• RSA Encryption Demo - simple RSA encryption of a string with a public key
• RSA Cryptography Demo - more complete demo of RSA encryption, decryption, and key generation
• ECDH Key Agreement Demo - Diffie-Hellman key agreement using elliptic curves

Source Code

  x = new BigInteger("abcd1234", 16);
  y = new BigInteger("beef", 16);
  z = x.mod(y);
  alert(z.toString(16));

Core Library

• jsbn.js - basic BigInteger implementation, just enough for RSA encryption and not much more.
• jsbn2.js - the rest of the library, including most public BigInteger methods.

RSA

• rsa.js - implementation of RSA encryption, does not require jsbn2.js.
• rsa2.js - rest of RSA algorithm, including decryption and keygen.

ECC

• ec.js - elliptic curve math, depends on both jsbn.js and jsbn2.js
• sec.js - standard elliptic curve parameters

Utilities

• rng.js - rudimentary entropy collector and RNG interface, requires a PRNG backend to define prng_newstate().
• prng4.js - ARC4-based PRNG backend for rng.js, very small.
• base64.js - Base64 encoding and decoding routines.
• sha1.js - SHA-1 hash function, only needed for IBE demo.

Interoperability

1. Generate a new public/private keypair:

   $ openssl genrsa -out key.pem
   Generating RSA private key, 512 bit long modulus
   ..++++++++++++
   ..............++++++++++++
   e is 65537 (0x10001)
   $
   

2. Extract the modulus from your key:

   $ openssl rsa -in key.pem -noout -modulus
   Modulus=DA3BB4C40E3C7E76F7DBDD8BF3DF0714CA39D3A0F7F9D7C2E4FEDF8C7B28C2875F7EB98950B22AE82D539C1ABC1AB550BA0B2D52E3EF7BDFB78A5E817D74BBDB
   $
   

3. Go to the RSA Encryption demo and paste the modulus value into the "Modulus (hex)" field at the bottom.
4. Make sure the value in the "Public exponent" field is "10001", or whatever value your public key uses.
5. Type in a short string (e.g. testing) into the "Plaintext (string)" field and click on "encrypt". The result should appear in the "Ciphertext" fields.
6. Copy the base64 version of the ciphertext and paste it as the input of the following command:

   $ openssl base64 -d | openssl rsautl -inkey key.pem -decrypt
   1JW24UMKntVhmmDilAYC1AjLxgiWHBzTzZsCVAejLjVri92abLHkSyLisVyAdYVr
   fiS7FchtI9vupe9JF/m3Kg==
   

   Hit ctrl-D or whatever your OS uses for end-of-file. Your original plaintext should appear:

   testing$
   

Performance

Projects that use jsbn

• Forge - a pure JavaScript implementation of SSL/TLS, includes a discussion of their choice of BigInteger library
• Dojo Toolkit uses jsbn in their dojox.math.BigInteger class.
• No More Cleartext Passwords - this project switched from another JavaScript BigInteger library for performance reasons
• Google's V8 benchmark suite, version 6
• JavaScript Cryptography Toolkit
• RSA-Sign JavaScript library
• JavaScript RSA

History

Version 1.4 (7/1/2013):

Fixed variable name collision between sha1.js and base64.js.

Obtain entropy from window.crypto.getRandomValues where available.

Added ECCurveFp.encodePointHex.

Fixed inconsistent use of DV in jsbn.js.

Version 1.3 (7/3/2012):

Fixed bug when comparing negative integers of different word lengths.

Version 1.2 (3/29/2011):

Added square method to improve ECC performance.

Use randomized bases in isProbablePrime

Version 1.1 (9/15/2009):

Added support for utf-8 encoding of non-ASCII characters when PKCS1 encoding and decoding JavaScript strings.

Fixed bug when creating a new BigInteger("0") in a non power-of-2 radix.

Licensing