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

If you are using CococaPods you must use pod cache clean IDZSwiftCommonCrypto --all after you upgrade Xcode. This is needed to avoid stale module maps being used from the CocoaPods cache. Removing your Podfile.lock and Pods directory is not sufficient.

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.

Which Release to Use

Which version you use depends on which version of Xcode and Swift you are currently using. Please refer to the list below:

• 0.7.4 -- Xcode 7.3.1, Swift 2.2
• 0.8.0 -- Xcode 7.3.1, Swift 2.2, with additional APIs for CCMode
• 0.8.3 -- Xcode 8.0, Swift 2.3
• 0.9.x -- Xcode 8.0, Swift 3.0
• 0.10.x -- Xcode 9.0, Swift 4.0
• 0.11.x -- Xcode 10.0, Swift 4.2
• 0.12.x -- Xcode 10.2, Swift 5.0
• 0.13.x -- Xcode 11.0, Swift 5.1, iOS 13.0

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 = arrayFrom(hexString: "0102030405060708090a0b0c0d0e0f10111213141516171819")
var datas5 : [UInt8] = Array(count:50, repeatedValue:0xcd)
var expecteds5 = arrayFrom(hexString: "4c9007f4026250c6bc8414f9bf50c86c2d7235da")
var hmacs5 = HMAC(algorithm:.sha1, key:keys5).update(datas5)?.final()

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

Supported Algorithms

• .md5
• .sha1
• .sha224
• .sha256
• .sha384
• .sha512

Using Cryptor

let algorithm = Cryptor.Algorithm.aes
var iv = try! Random.generateBytes(byteCount: algorithm.blockSize())
var key = arrayFrom(hexString: "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:algorithm, options:.PKCS7Padding, key:key, iv:iv)
var cipherText = cryptor.update(plainText)?.final()

cryptor = Cryptor(operation:.decrypt, algorithm:algorithm, options:.PKCS7Padding, key:key, iv:iv)
var decryptedPlainText = cryptor.update(cipherText!)?.final()
var decryptedString = String(bytes: decryptedPlainText!, encoding: .utf8)
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: InputStream, outputStream: OutputStream, bufferSize: Int) -> (bytesRead: Int, bytesWritten: Int)
{
    var inputBuffer = Array<UInt8>(repeating:0, count:1024)
    var outputBuffer = Array<UInt8>(repeating:0, count:1024)


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

let imagePath = Bundle.main.path(forResource: "Riscal", ofType:"jpg")!
let tmp = NSTemporaryDirectory() as NSString
let encryptedFilePath = "\(tmp)/Riscal.xjpgx"
var decryptedFilePath = "\(tmp)/RiscalDecrypted.jpg"

// Prepare the input and output streams for the encryption operation
guard let imageInputStream = InputStream(fileAtPath: imagePath) else {
    fatalError("Failed to initialize the image input stream.")
}
imageInputStream.open()
guard let  encryptedFileOutputStream = OutputStream(toFileAtPath: encryptedFilePath, append:false) else
{
    fatalError("Failed to open output stream.")
}
encryptedFileOutputStream.open()

// Generate a new, random initialization vector
let initializationVector = try! Random.generateBytes(byteCount: algorithm.blockSize())

// A common way to communicate the initialization vector is to write it at the beginning of the encrypted data.
let bytesWritten = encryptedFileOutputStream.write(initializationVector, maxLength: initializationVector.count)

// Now write the encrypted data
var sc = StreamCryptor(operation:.encrypt, algorithm:algorithm, options:.PKCS7Padding, key:key, iv:initializationVector)
guard  bytesWritten == initializationVector.count else
{
    fatalError("Failed to write initialization vector to encrypted output file.")
}
let outputResult = crypt(sc: sc, inputStream: imageInputStream, outputStream: encryptedFileOutputStream, bufferSize: 1024)
encryptedFileOutputStream.close()
outputResult

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

// Prepare the input and output streams for the decryption operation
guard let encryptedFileInputStream = InputStream(fileAtPath: encryptedFilePath) else
{
    fatalError("Failed to open the encrypted file for input.")
}
encryptedFileInputStream.open()
guard let decryptedFileOutputStream = OutputStream(toFileAtPath: decryptedFilePath, append:false) else {
    fatalError("Failed to open the file for the decrypted output file.")
}
decryptedFileOutputStream.open()

// Read back the initialization vector.
var readbackInitializationVector = Array<UInt8>(repeating: 0, count: algorithm.blockSize())
let bytesRead = encryptedFileInputStream.read(&readbackInitializationVector, maxLength: readbackInitializationVector.count)

// Uncomment this to verify that we did indeed read back the initialization vector.
//assert(readbackInitializationVector == initializationVector)

// Now use the read back initialization vector (along with the key) to
sc = StreamCryptor(operation:.decrypt, algorithm:algorithm, options:.PKCS7Padding, key:key, iv:readbackInitializationVector)
let inputResult = crypt(sc: sc, inputStream: encryptedFileInputStream, outputStream: decryptedFileOutputStream, bufferSize: 1024)

// Uncomment this to verify that decrypt operation consumed all the encrypted data
// and produced the correct number of bytes of plaintext output.
//assert(inputResult.bytesRead == outputResult.bytesWritten && inputResult.bytesWritten == outputResult.bytesRead)

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

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 = arrayFrom(hexString: "0c60c80f961f0e71f3a9b524af6012062fe037a6")
assert(keys6 == expectedRFC6070)

Supported Pseudo-Random Functions

• .sha1
• .sha224
• .sha256
• .sha384
• .sha512

GitHub

https://github.com/iosdevzone/IDZSwiftCommonCrypto