The purpose of this task to code and validate an implementation of the MD5 Message Digest Algorithm by coding the algorithm directly (not using a call to a built-in or external hashing library). For details of the algorithm refer to MD5 on Wikipedia or the MD5 definition in IETF RFC (1321).

 The implementation needs to implement the key functionality namely producing a correct message digest for an input string. It is not necessary to mimic all of the calling modes such as adding to a digest one block at a time over subsequent calls. 
 In addition to coding and verifying your implementation, note any challenges your language presented implementing the solution, implementation choices made, or limitations of your solution. 
 Solutions on this page should implement MD5 directly and NOT use built in (MD5) functions, call outs to operating system calls or library routines written in other languages as is common in the original MD5 task.
 The following are acceptable:
 An original implementation from the specification, reference implementation, or pseudo-code
 A translation of a correct implementation from another language
 A library routine in the same language; however, the source must be included here.


The solutions shown here will provide practical illustrations of bit manipulation, unsigned integers, working with little-endian data. Additionally, the task requires an attention to details such as boundary conditions since being out by even 1 bit will produce dramatically different results. Subtle implementation bugs can result in some hashes being correct while others are wrong. Not only is it critical to get the individual sub functions working correctly, even small errors in padding, endianness, or data layout will result in failure.

RFC 1321
                            hash code <== string 
   0xd41d8cd98f00b204e9800998ecf8427e <== ""  
   0x0cc175b9c0f1b6a831c399e269772661 <== "a"
   0x900150983cd24fb0d6963f7d28e17f72 <== "abc"
   0xf96b697d7cb7938d525a2f31aaf161d0 <== "message digest"
   0xc3fcd3d76192e4007dfb496cca67e13b <== "abcdefghijklmnopqrstuvwxyz"
   0xd174ab98d277d9f5a5611c2c9f419d9f <== "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
   0x57edf4a22be3c955ac49da2e2107b67a <== "12345678901234567890123456789012345678901234567890123456789012345678901234567890"
In addition, intermediate outputs to aid in developing an implementation can be found here.

The MD5 Message-Digest Algorithm was developed by RSA Data Security, Inc. in 1991.



 Warning
Rosetta Code is not a place you should rely on for examples of code in critical roles, including security.
Also, note that MD5 has been broken and should not be used in applications requiring security. For these consider SHA2 or the upcoming SHA3.

 
    import Foundation
    public class MD5 {
        /** specifies the per-round shift amounts */
        private let s: [UInt32] = [7, 12, 17, 22,  7, 12, 17, 22,  7, 12, 17, 22,  7, 12, 17, 22,
                           5,  9, 14, 20,  5,  9, 14, 20,  5,  9, 14, 20,  5,  9, 14, 20,
                           4, 11, 16, 23,  4, 11, 16, 23,  4, 11, 16, 23,  4, 11, 16, 23,
                           6, 10, 15, 21,  6, 10, 15, 21,  6, 10, 15, 21,  6, 10, 15, 21]
 
        /** binary integer part of the sines of integers (Radians) */
        private let K: [UInt32] = (0 ..< 64).map { UInt32(0x100000000 * abs(sin(Double($0 + 1)))) }
 
        let a0: UInt32 = 0x67452301
        let b0: UInt32 = 0xefcdab89
        let c0: UInt32 = 0x98badcfe
        let d0: UInt32 = 0x10325476
 
        private var message: NSData
 
        //MARK: Public
 
        public init(_ message: NSData) {
            self.message = message
        }
 
        public func calculate() -> NSData? {
            var tmpMessage: NSMutableData = NSMutableData(data: message)
            let wordSize = sizeof(UInt32)
 
            var aa = a0
            var bb = b0
            var cc = c0
            var dd = d0
 
            // Step 1. Append Padding Bits
            tmpMessage.appendBytes([0x80]) // append one bit (Byte with one bit) to message
 
            // append "0" bit until message length in bits ≡ 448 (mod 512)
            while tmpMessage.length % 64 != 56 {
                tmpMessage.appendBytes([0x00])
            }
 
            // Step 2. Append Length a 64-bit representation of lengthInBits
            var lengthInBits = (message.length * 8)
            var lengthBytes = lengthInBits.bytes(64 / 8)
            tmpMessage.appendBytes(reverse(lengthBytes));
 
            // Process the message in successive 512-bit chunks:
            let chunkSizeBytes = 512 / 8
            var leftMessageBytes = tmpMessage.length
            for var i = 0; i < tmpMessage.length; i = i + chunkSizeBytes, leftMessageBytes -= chunkSizeBytes {
                let chunk = tmpMessage.subdataWithRange(NSRange(location: i, length: min(chunkSizeBytes,leftMessageBytes)))
 
                // break chunk into sixteen 32-bit words M[j], 0 ≤ j ≤ 15
                // println("wordSize \(wordSize)");
                var M:[UInt32] = [UInt32](count: 16, repeatedValue: 0)
                for x in 0..<M.count {
                    var range = NSRange(location:x * wordSize, length: wordSize)
                    chunk.getBytes(&M[x], range:range);
                }
 
                // Initialize hash value for this chunk:
                var A:UInt32 = a0
                var B:UInt32 = b0
                var C:UInt32 = c0
                var D:UInt32 = d0
 
                var dTemp:UInt32 = 0
 
                // Main loop
                for j in 0...63 {
                    var g = 0
                    var F:UInt32 = 0
 
                    switch (j) {
                    case 0...15:
                        F = (B & C) | ((~B) & D)
                        g = j
                        break
                    case 16...31:
                        F = (D & B) | (~D & C)
                        g = (5 * j + 1) % 16
                        break
                    case 32...47:
                        F = B ^ C ^ D
                        g = (3 * j + 5) % 16
                        break
                    case 48...63:
                        F = C ^ (B | (~D))
                        g = (7 * j) % 16
                        break
                    default:
                        break
                    }
                    dTemp = D
                    D = C
                    C = B
                    B = B &+ rotateLeft((A &+ F &+ K[j] &+ M[g]), s[j])
                    A = dTemp    
                }
 
                aa = aa &+ A
                bb = bb &+ B
                cc = cc &+ C
                dd = dd &+ D
            }
 
            var buf: NSMutableData = NSMutableData();
            buf.appendBytes(&aa, length: wordSize)
            buf.appendBytes(&bb, length: wordSize)
            buf.appendBytes(&cc, length: wordSize)
            buf.appendBytes(&dd, length: wordSize)
 
            return buf.copy() as? NSData;
        }
 
        //MARK: Class
        class func calculate(message: NSData) -> NSData?
        {
            return MD5(message).calculate();
        }
 
        //MARK: Private
        private func rotateLeft(x:UInt32, _ n:UInt32) -> UInt32 {
            return (x &<< n) | (x &>> (32 - n))
        }
    }
 