SubtleCrypto javascript example

SubtleCrypto.js

// exemple based on https://github.com/diafygi/webcrypto-examples#rsa-oaep

function importKey() {
	return window.crypto.subtle.importKey(
	    "jwk", //can be "jwk" or "raw"
	    {   //this is an example jwk key, "raw" would be an ArrayBuffer
	        kty: "oct",
	        k: "Y0zt37HgOx-BY7SQjYVmrqhPkO44Ii2Jcb9yydUDPfE",
	        alg: "A256GCM",
	        ext: true,
	    },
	    {   //this is the algorithm options
	        name: "AES-GCM",
	    },
	    false, //whether the key is extractable (i.e. can be used in exportKey)
	    ["encrypt", "decrypt"] //can "encrypt", "decrypt", "wrapKey", or "unwrapKey"
	)
}

function generateKey() {
	return window.crypto.subtle.generateKey(
	    {
	        name: "AES-GCM",
	        length: 256, //can be  128, 192, or 256
	    },
	    true, //whether the key is extractable (i.e. can be used in exportKey)
	    ["encrypt", "decrypt"] //can "encrypt", "decrypt", "wrapKey", or "unwrapKey"
	)
}

function encrypt(data, key, iv) {
	return window.crypto.subtle.encrypt(
	    {
	        name: "AES-GCM",

	        //Don't re-use initialization vectors!
	        //Always generate a new iv every time your encrypt!
	        //Recommended to use 12 bytes length
	        iv: iv,

	        //Additional authentication data (optional)
	        // additionalData: ArrayBuffer,

	        //Tag length (optional)
	        tagLength: 128, //can be 32, 64, 96, 104, 112, 120 or 128 (default)
	    },
	    key, //from generateKey or importKey above
	    data //ArrayBuffer of data you want to encrypt
	)
}

function decrypt(data, key, iv) {
	return window.crypto.subtle.decrypt(
	    {
	        name: "AES-GCM",
	        iv: iv, //The initialization vector you used to encrypt
	        //additionalData: ArrayBuffer, //The addtionalData you used to encrypt (if any)
	        tagLength: 128, //The tagLength you used to encrypt (if any)
	    },
	    key, //from generateKey or importKey above
	    data //ArrayBuffer of the data
	)
}
var keys = await importKey()
var iv   = new Uint8Array([188, 185, 57, 146, 246, 194, 114, 34, 12, 80, 198, 77])
var enc  = new TextEncoder();
var data = enc.encode("This is a secret message")
var encryptedData = await encrypt(data, keys, iv)
var decryptedData = await decrypt(encryptedData, keys, iv)
var enc = new TextDecoder("utf-8");
enc.decode(decryptedData)