import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.Security;

import org.apache.commons.codec.binary.Hex;

public class CryptoHashTest {


	public static byte[] md5(byte[] input) {
		//Note: All variables are unsigned 32 bit and wrap modulo 2^32 when calculating
		int[64] K
		int i

		//s specifies the per-round shift amounts
		int[] s = { 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 };

		//Use binary integer part of the sines of integers (Radians) as constants:
		for i from 0 to 63
		    K[i] := floor(232 × abs(sin(i + 1)))
		end for
		//(Or just use the following precomputed table):
		K[ 0.. 3] := { 0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee }
		K[ 4.. 7] := { 0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501 }
		K[ 8..11] := { 0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be }
		K[12..15] := { 0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821 }
		K[16..19] := { 0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa }
		K[20..23] := { 0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8 }
		K[24..27] := { 0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed }
		K[28..31] := { 0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a }
		K[32..35] := { 0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c }
		K[36..39] := { 0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70 }
		K[40..43] := { 0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05 }
		K[44..47] := { 0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665 }
		K[48..51] := { 0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039 }
		K[52..55] := { 0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1 }
		K[56..59] := { 0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1 }
		K[60..63] := { 0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391 }

		//Initialize variables:
		var int a0 := 0x67452301   //A
		var int b0 := 0xefcdab89   //B
		var int c0 := 0x98badcfe   //C
		var int d0 := 0x10325476   //D

		//Pre-processing: adding a single 1 bit
		append "1" bit to message    
		// Notice: the input bytes are considered as bits strings,
		//  where the first bit is the most significant bit of the byte.[49]

		//Pre-processing: padding with zeros
		append "0" bit until message length in bits ≡ 448 (mod 512)
		append original length in bits mod 264 to message

		//Process the message in successive 512-bit chunks:
		for each 512-bit chunk of padded message
		    break chunk into sixteen 32-bit words M[j], 0 ≤ j ≤ 15
		    //Initialize hash value for this chunk:
		    var int A := a0
		    var int B := b0
		    var int C := c0
		    var int D := d0
		    //Main loop:
		    for i from 0 to 63
		        var int F, g
		        if 0 ≤ i ≤ 15 then
		            F := (B and C) or ((not B) and D)
		            g := i
		        else if 16 ≤ i ≤ 31 then
		            F := (D and B) or ((not D) and C)
		            g := (5×i + 1) mod 16
		        else if 32 ≤ i ≤ 47 then
		            F := B xor C xor D
		            g := (3×i + 5) mod 16
		        else if 48 ≤ i ≤ 63 then
		            F := C xor (B or (not D))
		            g := (7×i) mod 16
		        //Be wary of the below definitions of a,b,c,d
		        F := F + A + K[i] + M[g]
		        A := D
		        D := C
		        C := B
		        B := B + leftrotate(F, s[i])
		    end for
		    //Add this chunk's hash to result so far:
		    a0 := a0 + A
		    b0 := b0 + B
		    c0 := c0 + C
		    d0 := d0 + D
		end for

		var char digest[16] := a0 append b0 append c0 append d0 //(Output is in little-endian)

		//leftrotate function definition
		leftrotate (x, c)
		    return (x << c) binary or (x >> (32-c));
	}
	
	public static void main(String[] args) throws NoSuchAlgorithmException {

		for (String s : Security.getAlgorithms("MessageDigest")) {
			System.out.println(s);
		}

		MessageDigest md5 = MessageDigest.getInstance("MD5");
		byte[] digest = md5.digest("Hello Digest".getBytes());
		System.out.println(Hex.encodeHex(digest));

		MessageDigest sha = MessageDigest.getInstance("SHA");
		digest = sha.digest("Hello Digest".getBytes());
		System.out.println(Hex.encodeHex(digest));
	}
}
