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Encryption and Decryption

I put together some examples of encrpting and decrypting information with javascript.

I use an XOR cipher where the key is the same length as the text.

I believe that these methods are cryptographically secure, but I make no guarantees. See this link for more information. Note: The linked website talks about a repeated xor cipher. This example does not repeat the key; the key is the same length as the plaintext/cyphertext.

Upon encryption, a random key is generated.

An example of how to encypt sensitive data is located at /secured.js.

All data stays on your device.

Encryption


function encrypt(plainText){
 //turn plainText into a uint8Array
 plainText = new TextEncoder().encode(plainText);
 
 //Pick a random key
 key = new Uint8Array(plainText.length)
 self.crypto.getRandomValues(key);
 
 //encrypt each array element one by one
 cypherText = new Uint8Array(plainText.length)
 for(i=0; i<cypherText.length; i++) cypherText[i] = (plainText[i] ^ key[i]);
 
 //convert cypherText and the random key to base64, then return them in a dictionary.
 cypherText = btoa(String.fromCharCode.apply(null, cypherText))
 key = btoa(String.fromCharCode.apply(null, key))
 return {"cypherText":cypherText,"key":key}
}

Decryption


function decrypt(cypherText, key){
 //decode cypherText and key from base64
 cypherText = atob(cypherText).split('').map(function (c) { return c.charCodeAt(0); });
 key = atob(key).split('').map(function (c) { return c.charCodeAt(0); });
 
 //turn cypherText into a uint8Array, each element one by one
 decodedText = new Uint8Array(cypherText.length)
 for(i=0; i<cypherText.length; i++) decodedText[i] = (cypherText[i] ^ key[i]);
 
 //return the decoded text
 return new TextDecoder().decode(decodedText);
}