combined RC4 RSA encrypt/decrypt for long messages Javascript

问题

NOTE: Yes, I understand there is a lot of code in this message, but you do encourage us to show prior research and how we've been trying.

Let me preface this by saying, I am not interested in the security of this function. All I want is to encrypt and decrypt arbitrarily long messages using RSA. Usually to do this, the message is encrypted using a block cipher (such as AES) and encrypting the key with the RSA cipher. However, I am just trying to find the easiest way to encrypt/decrypt long messages, irregardless of security. Hence why I am using RC4 in place of the block cipher.

Now, I can encrypt properly using the following code:

function encryptLong(signedCert, msg) {
var key256Bits = CryptoJS.SHA256("password");
var ciphertext = CryptoJS.RC4.encrypt(msg, key256Bits);
key = new RSAKey();
var m = CryptoJS.SHA256("password").toString(CryptoJS.enc.Hex);
m = new BigInteger(m, 16);
key.setPublic(signedCert.msg.subject.pk.n, signedCert.msg.subject.pk.e);
var ctxt = key.doPublic(m).toString(16);
var cipherstring = ciphertext + ":" + ctxt;
var obj = { "type": "CTXT-LONG", "encrypted": cipherstring };
return JSON.stringify(obj);
}

The message and the key are encrypted properly. I tested them individually using these functions.

function encryptRSA(signedCert, msg) {
//create a new RSA key object
var key = new RSAKey();
//convert ASCII message to hex
var m = asciiToHex(msg);
// create new BigInterger from m
m = new BigInteger(m, 16);
// set the values for the public key
key.setPublic(signedCert.msg.subject.pk.n, signedCert.msg.subject.pk.e);
// compute the RSA public key operation, and convert to a hex value
var ctxt = key.doPublic(m).toString(16);
//enter ctxt into the JSON obj
var obj = { "type": "CTXT-SHORT", "c": ctxt };
return JSON.stringify(obj);
}

And...

function encryptRSA(password, message) {
var key256Bits = CryptoJS.SHA256(password);
var ciphertext = CryptoJS.RC4.encrypt(CryptoJS.enc.Utf8.parse(message), key256Bits);
return ciphertext;
}

Now, here is our decryption code:

function decryptLong(sk, ctxt) {
key = new RSAKey();
encryptedStuff = JSON.stringify(ctxt.encrypted);
log(encryptedStuff);
splitEncryptedstuff = encryptedStuff.split(":");
rsaencryption = splitEncryptedstuff[1];
log(rsaencryption);
rc4encryption = splitEncryptedstuff[0];
log(rc4encryption);
c = new BigInteger(rsaencryption, 16);
key.setPrivate(sk.n, sk.e, sk.d);
var key256Bits = key.doPrivate(c).toString(16);
log(key256Bits);
// RC4 decryption
var message = CryptoJS.RC4.decrypt(rc4encryption, key224Bits);
// var ptxt = CryptoJS.enc.Utf8.stringify(message);
// log(ptxt);
return CryptoJS.enc.Utf8.stringify(message);
}

This code doesn't decrypt properly, but I know parts of it work. For example, where I have

log(key356Bits);

it returns the key exactly. So I know that at least the RSA decryption works. What I don't understand is, I followed the decryption function that I have exactly. Which is as follows.

function decryptRC4(password, ciphertext) {
var key256Bits = CryptoJS.SHA256(password);
var message = CryptoJS.RC4.decrypt(ciphertext, key256Bits);
return CryptoJS.enc.Utf8.stringify(message);
}

Well not exactly, I don't have to take the Hash of the password to get the key, as I already have the key. But, I still don't understand what is not working. When we decrypt our ciphertext using this individual function, the plaintext is correct.

Any assistance in this matter would be greatly appreciated.

Knowing my luck, it's probably just something annoying like it's in the wrong encoding type thing.

来源：https://stackoverflow.com/questions/19565089/combined-rc4-rsa-encrypt-decrypt-for-long-messages-javascript