IDZSwiftCommonCrypto

A Swift wrapper for Apple's CommonCrypto library.

IDZSwiftCommonCrypto works with both CocoaPods and Cathage. For more details on how to install it into your projects see INSTALL.md

IDZSwiftCommonCrypto provides the following classes:

• Digest for calculating message digests,
• HMAC for calculating Hash-based Message Authentication Codes,
• Cryptor for encrypting and decrypting bounded buffers,
• StreamCryptor for encrypting and decrypting streaming information, and
• PBKDF for deriving key material from a password or passphrase.

Using Digest

To calculate a message digest you create an instance of Digest, call update one or more times with the data over which the digest is being calculated and finally call final to obtain the digest itself.

The update method can take a String

let  s = "The quick brown fox jumps over the lazy dog."
var md5s2 : Digest = Digest(algorithm:.MD5)
md5s2.update(s)
let digests2 = md5s2.final()

// According to Wikipedia this should be
// e4d909c290d0fb1ca068ffaddf22cbd0
hexStringFromArray(digests2)
assert(digests2 == arrayFromHexString("e4d909c290d0fb1ca068ffaddf22cbd0"))

or an array of UInt8 elements:

let b : [UInt8] = 
[0x54,0x68,0x65,0x20,0x71,0x75,0x69,0x63,
0x6b,0x20,0x62,0x72,0x6f,0x77,0x6e,0x20,
0x66,0x6f,0x78,0x2e]
var md5s1 : Digest = Digest(algorithm:.MD5)
md5s1.update(b)
let digests1 = md5s1.final()

If you only have a single buffer you can simply write

  var digests3 = Digest(algorithm: .MD5).update(b)?.final() // digest is of type [UInt8]?

or

  var digests4 = Digest(algorithm: .MD5).update(s)?.final() // digest is of type [UInt8]?

Supported Algorithms

The Digest class supports the following algorithms:

• .MD2
• .MD4
• .MD5
• .SHA1
• .SHA224
• .SHA256
• .SHA384
• .SHA512

Using HMAC

Calculating a keyed-Hash Message Authentication Code (HMAC) is very similar to calculating a message digest, except that the initialization routine now takes a key as well as an algorithm parameter.

var keys5 = arrayFromHexString("0102030405060708090a0b0c0d0e0f10111213141516171819")
var datas5 : [UInt8] = Array(count:50, repeatedValue:0xcd)
var expecteds5 = arrayFromHexString("4c9007f4026250c6bc8414f9bf50c86c2d7235da")
var hmacs5 = HMAC(algorithm:.SHA1, key:keys5).update(datas5)?.final()

// RFC2202 says this should be 4c9007f4026250c6bc8414f9bf50c86c2d7235da
let expectedRFC2202 = arrayFromHexString("4c9007f4026250c6bc8414f9bf50c86c2d7235da")
assert(hmacs5! == expectedRFC2202)

Supported Algorithms

• SHA1
• MD5
• SHA224
• SHA256
• SHA384
• SHA512

Using Cryptor

var key = arrayFromHexString("2b7e151628aed2a6abf7158809cf4f3c")
var plainText = "The quick brown fox jumps over the lazy dog. The fox has more or less had it at this point."

var cryptor = Cryptor(operation:.Encrypt, algorithm:.AES, options:.PKCS7Padding, key:key, iv:Array<UInt8>())
var cipherText = cryptor.update(plainText)?.final()

cryptor = Cryptor(operation:.Decrypt, algorithm:.AES, options:.PKCS7Padding, key:key, iv:Array<UInt8>())
var decryptedPlainText = cryptor.update(cipherText!)?.final()
var decryptedString = decryptedPlainText!.reduce("") { $0 + String(UnicodeScalar($1)) }
decryptedString
assert(decryptedString == plainText)

Supported Algorithms

• .AES
• .DES
• .TripleDES
• .CAST
• .RC2
• .Blowfish

Using StreamCryptor

To encrypt a large file or a network stream use StreamCryptor. The StreamCryptor class does not accumulate the encrypted or decrypted data, instead each call to update produces an output buffer.

The example below shows how to use StreamCryptor to encrypt and decrypt an image file.

func crypt(sc : StreamCryptor,  inputStream: NSInputStream, outputStream: NSOutputStream, bufferSize: Int)
{
    var inputBuffer = Array<UInt8>(count:1024, repeatedValue:0)
    var outputBuffer = Array<UInt8>(count:1024, repeatedValue:0)
    inputStream.open()
    outputStream.open()

    var cryptedBytes : UInt = 0    
    while inputStream.hasBytesAvailable
    {
        let bytesRead = inputStream.read(&inputBuffer, maxLength: inputBuffer.count)
        let status = sc.update(inputBuffer, byteCountIn: UInt(bytesRead), bufferOut: &outputBuffer, byteCapacityOut: UInt(outputBuffer.count), byteCountOut: &cryptedBytes)
        assert(status == Status.Success)
        if(cryptedBytes > 0)
        {
            let bytesWritten = outputStream.write(outputBuffer, maxLength: Int(cryptedBytes))
            assert(bytesWritten == Int(cryptedBytes))
        }
    }
    let status = sc.final(&outputBuffer, byteCapacityOut: UInt(outputBuffer.count), byteCountOut: &cryptedBytes)    
    assert(status == Status.Success)
    if(cryptedBytes > 0)
    {
        let bytesWritten = outputStream.write(outputBuffer, maxLength: Int(cryptedBytes))
        assert(bytesWritten == Int(cryptedBytes))
    }
    inputStream.close()
    outputStream.close()
}

let imagePath = NSBundle.mainBundle().pathForResource("Riscal", ofType:"jpg")!
let tmp = NSTemporaryDirectory()
let encryptedFilePath = tmp.stringByAppendingPathComponent("Riscal.xjpgx")
var decryptedFilePath = tmp.stringByAppendingPathComponent("RiscalDecrypted.jpg")

var imageInputStream = NSInputStream(fileAtPath: imagePath)
var encryptedFileOutputStream = NSOutputStream(toFileAtPath: encryptedFilePath, append:false)
var encryptedFileInputStream = NSInputStream(fileAtPath: encryptedFilePath)
var decryptedFileOutputStream = NSOutputStream(toFileAtPath: decryptedFilePath, append:false)

var sc = StreamCryptor(operation:.Encrypt, algorithm:.AES, options:.PKCS7Padding, key:key, iv:Array<UInt8>())
crypt(sc, imageInputStream, encryptedFileOutputStream, 1024)

// Uncomment this line to verify that the file is encrypted
//var encryptedImage = UIImage(contentsOfFile:encryptedFile)

sc = StreamCryptor(operation:.Decrypt, algorithm:.AES, options:.PKCS7Padding, key:key, iv:Array<UInt8>())
crypt(sc, encryptedFileInputStream, decryptedFileOutputStream, 1024)

var image = UIImage(named:"Riscal.jpg")
var decryptedImage = UIImage(contentsOfFile:decryptedFilePath)

Using PBKDF

The PBKDF class provides a method of deriving keys from a user password. The following example derives a 20-byte key:

let keys6 = PBKDF.deriveKey("password", salt: "salt", prf: .SHA1, rounds: 1, derivedKeyLength: 20)
// RFC 6070 - Should derive 0c60c80f961f0e71f3a9b524af6012062fe037a6
let expectedRFC6070 = arrayFromHexString("0c60c80f961f0e71f3a9b524af6012062fe037a6")
assert(keys6 == expectedRFC6070)

Supported Pseudo-Random Functions

• .SHA1
• .SHA224
• .SHA256
• .SHA384
• .SHA512