implemented wrapper for symmetric nacl encryption

src/js/crypto/nacl-crypto.js

@@ -38,8 +38,9 @@ var NaclCrypto = function(nacl, util) {
 		var senderBoxSkBuf = nacl.encode_latin1(util.base642Str(senderBoxSk));
 		// generate nonce
 		var nonce = nacl.crypto_secretbox_random_nonce();
-
+		// encrypt
 		var ct = nacl.crypto_box(ptBuf, nonce, recipientBoxPkBuf, senderBoxSkBuf);
+		// encode to base64
 		var ctBase64 = util.str2Base64(nacl.decode_latin1(ct));
 		var nonceBase64 = util.str2Base64(nacl.decode_latin1(nonce));
 
@@ -63,8 +64,53 @@ var NaclCrypto = function(nacl, util) {
 		var nonceBuf = nacl.encode_latin1(util.base642Str(nonce));
 		var senderBoxPkBuf = nacl.encode_latin1(util.base642Str(senderBoxPk));
 		var recipientBoxSkBuf = nacl.encode_latin1(util.base642Str(recipientBoxSk));
-
+		// decrypt
 		var pt = nacl.crypto_box_open(ctBuf, nonceBuf, senderBoxPkBuf, recipientBoxSkBuf);
+		// decode to string
+		var ptStr = nacl.decode_utf8(pt);
+
+		return ptStr;
+	};
+
+	/**
+	 * Symmetrically encrypt a String
+	 * @param plaintext [String] The input string in UTF8
+	 * @param secretKey [String] The receiver's base64 encoded public key
+	 * @return [Object] The base64 encoded ciphertext and nonce
+	 */
+	this.symmetricEncrypt = function(plaintext, secretKey) {
+		// convert to Uint8Array
+		var ptBuf = nacl.encode_utf8(plaintext);
+		var secretKeyBuf = nacl.encode_latin1(util.base642Str(secretKey));
+		// generate nonce
+		var nonce = nacl.crypto_secretbox_random_nonce();
+		// encrypt
+		var ct = nacl.crypto_secretbox(ptBuf, nonce, secretKeyBuf);
+		// encode to base64
+		var ctBase64 = util.str2Base64(nacl.decode_latin1(ct));
+		var nonceBase64 = util.str2Base64(nacl.decode_latin1(nonce));
+
+		return {
+			ct: ctBase64,
+			nonce: nonceBase64
+		};
+	};
+
+	/**
+	 * Symmetrically decrypt a String
+	 * @param ciphertext [String] The base64 encoded ciphertext
+	 * @param nonce [String] The base64 encoded nonce
+	 * @param secretKey [String] The sender's base64 encoded public key
+	 * @return [String] The decrypted plaintext in UTF8
+	 */
+	this.symmetricDecrypt = function(ciphertext, nonce, secretKey) {
+		// convert to Uint8Array
+		var ctBuf = nacl.encode_latin1(util.base642Str(ciphertext));
+		var nonceBuf = nacl.encode_latin1(util.base642Str(nonce));
+		var secretKeyBuf = nacl.encode_latin1(util.base642Str(secretKey));
+		// decrypt
+		var pt = nacl.crypto_secretbox_open(ctBuf, nonceBuf, secretKeyBuf);
+		// decode to string
 		var ptStr = nacl.decode_utf8(pt);
 
 		return ptStr;

test/unit/nacl-crypto-test.js

@@ -31,7 +31,7 @@ test("Generate Keypair", 2, function() {
 	nacl_test.recipientKeypair = recipientKeypair;
 });
 
-test("En/Decrypt", 2, function() {
+test("Asymmetric En/Decrypt", 2, function() {
 	var plaintext = nacl_test.test_message;
 
 	// encrypt
@@ -41,4 +41,17 @@ test("En/Decrypt", 2, function() {
 	// decrypt
 	var decrypted = nacl_test.crypto.asymmetricDecrypt(ct.ct, ct.nonce, nacl_test.senderKeypair.boxPk, nacl_test.recipientKeypair.boxSk);
 	equal(decrypted, plaintext, 'Decryption correct: ' + decrypted);
+});
+
+test("Symmetric En/Decrypt", 2, function() {
+	var plaintext = nacl_test.test_message;
+
+	// encrypt
+	var ct = nacl_test.crypto.symmetricEncrypt(plaintext, nacl_test.senderKeypair.boxSk);
+	ok(ct.ct && ct.nonce, 'Ciphertext length: ' + ct.ct.length);
+
+	// decrypt
+	var decrypted = nacl_test.crypto.symmetricDecrypt(ct.ct, ct.nonce, nacl_test.senderKeypair.boxSk);
+	equal(decrypted, plaintext, 'Decryption correct: ' + decrypted);
+
 });