Node.js Crypto (RC4)

Theory

A sample run is:

Message:         test
Passphrase:      test
Ciphertext:      83d2e09c
Decipher:        test

The following is some sample code

// RC4

var crypto = require('crypto');

var keyname="test";
var plaintext = "testing";

var args = process.argv;
if (args.length>1) plaintext=args[2];
if (args.length>2) keyname=args[3];

var key = crypto.createHash('sha256').update(keyname).digest();

var cipher = crypto.createCipheriv('rc4', key,'' );
var ciphertext = cipher.update( plaintext, 'utf8', 'hex');
console.log("Ciphertext:\t",ciphertext);


var decipher = crypto.createDecipheriv('rc4', key,'' );
var text = decipher.update( ciphertext, 'hex','utf8');
console.log("Decipher:\t",text);

For a password of "napier, a range of fruits have been ciphered using the RC4 cipher stream:

8d1cc8bdf6da
911adbb2e6dda57cdaad
8907deba

Answer these:

• What are the fruits?
• What happens to the cipher when you add an IV (salt) string?
• For light-weight cryptography, what is the advantage of having a variable key size:
• How might we change the program to implement 128-bit RC4?