/*
* ---------------------------------------------------------
* NetSHA.SHA256 .Net Framework implementation of SHA-256
*
* by Jarrod Nelson for ECE 575 Project
* ---------------------------------------------------------
* Comments:
* This class contains static methods which
* implement SHA-256 either on a given file or on
* a message stored in a byte array.
* ---------------------------------------------------------
*
*/
// http://islab.oregonstate.edu/koc/ece575/04Project/Nelson/NetSHA.htm
using System;
//using System.IO;
namespace sc
{
/// <summary>
/// SHA-256 implementation
/// </summary>
public sealed class SHA256
{
//SHA-256 constants
private const uint _H00 = 0x6a09e667;
private const uint _H10 = 0xbb67ae85;
private const uint _H20 = 0x3c6ef372;
private const uint _H30 = 0xa54ff53a;
private const uint _H40 = 0x510e527f;
private const uint _H50 = 0x9b05688c;
private const uint _H60 = 0x1f83d9ab;
private const uint _H70 = 0x5be0cd19;
/// <summary>
/// This method take a byte array, pads it according to the
/// specifications in FIPS 180-2 and passes to the SHA-256
/// hash function. It returns a byte array containing
/// the hash of the given message.
/// </summary>
/// <param name="message">Message to be hashed as byte array</param>
/// <returns>Message hash value as byte array</returns>
public static byte[] MessageSHA256( byte[] message )
{
int n, pBase;
long l;
byte[] m;
byte[] pad;
byte[] swap;
byte[] temp;
// Determine length of message in 512-bit blocks
n = (int)(message.Length >> 6);
// Determine space required for padding
if( (message.Length & 0x3f) < 56 )
{
n++;
pBase = 56;
}
else
{
n+=2;
pBase = 120;
}
// Determine total message length
l = message.Length << 3;
// Create message padding
pad = new byte[pBase-(message.Length & 0x3f)];
pad[0] = 0x80;
for( int i = 1; i < pad.Length; i++ )
pad[i] = 0;
m = new byte[n*64];
// Assemble padded message
Array.Copy( message, 0, m, 0, message.Length );
Array.Copy( pad, 0, m, message.Length, pad.Length );
temp = BitConverter.GetBytes( (long)l );
swap = new byte[8];
for( int i = 0; i < 8; i++ )
swap[i] = temp[7-i];
Array.Copy( swap, 0, m, message.Length+pad.Length, 8 );
// Call Hash1 to hash message
return Hash256( n, m );
}
/*
/// <summary>
/// This methods takes the name of a file containing
/// a message to be hashed. It loads the message and
/// calls MessageSHA256 to pad and hash the message. This
/// method returns a byte array containing the hash value
/// for the given file.
/// </summary>
/// <param name="fileName">
/// Name of file containing message to be hashed.
/// </param>
/// <returns>Message hash value as byte array</returns>
public static byte[] FileSHA256( string fileName )
{
byte[] m;
// Open File and read in message
FileStream messageFile = new FileStream( fileName,
FileMode.Open, FileAccess.Read );
// Check length of file to ensure it is within
// currently supported range.
if( Int32.MaxValue > messageFile.Length )
{
m = new byte[ (int)messageFile.Length-2 ];
messageFile.Read( m, 0, (int)messageFile.Length-2 );
}
else
throw new Exception( "File length exceeds current supported size!" );
messageFile.Close();
// Call MessageSHA1
return MessageSHA256( m );
}
*/
/// <summary>
/// SHA-1 Hash function - This method should only be used
/// with properly padded messages. To hash an unpadded
/// message use one of the other methods. This method is
/// called by other methods once the message is padded
/// and loaded as a byte array. For internal use only!
/// </summary>
/// <param name="n">Number of 512-bit message segments</param>
/// <param name="m">Message to be hashed as byte array</param>
/// <returns>Hash value as byte array</returns>
private static byte[] Hash256( int n, byte[] m )
{
// K Constants
uint[] K = { 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2 };
// Calculation variables
uint a, b, c, d, e, f, g, h, temp1, temp2;
// Intermediate hash values
uint[] interHash = new uint[8];
// Scheduled W values
uint[] w = new uint[64];
// Final hash byte array
byte[] hash = new byte[32];
// Used to correct for endian
byte[] swap = new byte[4];
byte[] swap2 = new byte[4];
// Initial hash values
interHash[0] = _H00;
interHash[1] = _H10;
interHash[2] = _H20;
interHash[3] = _H30;
interHash[4] = _H40;
interHash[5] = _H50;
interHash[6] = _H60;
interHash[7] = _H70;
// Perform hash operation
for( int i = 0; i < n; i++ )
{
// Prepare the message schedule
for( int t = 0; t < 64; t++ )
{
if( t < 16 )
{
for( int j = 0; j < 4; j++ )
swap[j] = m[i*64+t*4+3-j];
w[t] = BitConverter.ToUInt32( swap, 0 );
}
else
{
w[t] = (uint)( Sigma( 3, w[t-2] ) + w[t-7]
+ Sigma( 2, w[t-15] ) + w[t-16] );
}
}
//Initialize the five working variables
a = interHash[0];
b = interHash[1];
c = interHash[2];
d = interHash[3];
e = interHash[4];
f = interHash[5];
g = interHash[6];
h = interHash[7];
//Perform main hash loop
for( int t = 0; t < 64; t++ )
{
temp1 = (uint)( h + Sigma( 1, e ) + Func(true, e, f, g)
+ K[t] + w[t] );
temp2 = (uint)( Sigma( 0, a ) + Func(false, a, b, c ) );
h = g;
g = f;
f = e;
e = (uint)( d + temp1 );
d = c;
c = b;
b = a;
a = (uint)( temp1 + temp2 );
}
//Compute the intermediate hash values
interHash[0] = (uint)( (a + interHash[0]) );
interHash[1] = (uint)( (b + interHash[1]) );
interHash[2] = (uint)( (c + interHash[2]) );
interHash[3] = (uint)( (d + interHash[3]) );
interHash[4] = (uint)( (e + interHash[4]) );
interHash[5] = (uint)( (f + interHash[5]) );
interHash[6] = (uint)( (g + interHash[6]) );
interHash[7] = (uint)( (h + interHash[7]) );
}
// Copy Intermediate results to final hash array
for( int i = 0; i < 8; i++)
{
swap2 = BitConverter.GetBytes( (uint) interHash[i] );
for( int j = 0; j < 4; j++ )
{
swap[j] = swap2[3-j];
}
Array.Copy( swap, 0, hash, i*4, 4 );
}
return hash;
}
/// <summary>
/// Performs SHA-256 logical functions. See FIPS 180-2 for
/// complete description. For internal use only!
/// </summary>
/// <param name="b">
/// Boolean value indicating whether the desired function is Ch
/// </param>
/// <param name="x">First arguement</param>
/// <param name="y">Second arguement</param>
/// <param name="z">Third arguement</param>
/// <returns>Function results</returns>
private static uint Func( bool b, uint x, uint y, uint z )
{
// Ch function
if( b )
return (uint)( (x & y) ^ ((~x) & z) );
// Maj function
return (uint)( (x & y) ^ (x & z) ^ (y & z) );
}
/// <summary>
/// Performs the SHA-256 shifting and rotating functions.
/// See FIPS 180-2 for complete details. For internal
/// use only!
/// </summary>
/// <param name="i">Integer indicating which function to perform</param>
/// <param name="x">Operand</param>
/// <returns>Result of rotation/shift</returns>
private static uint Sigma( int i, uint x )
{
uint temp;
switch( i )
{
case 0:
temp = (uint)( (x>>2) | (x<<30) );
temp = temp ^ (uint)( (x>>13) | (x<<19) );
temp = temp ^ (uint)( (x>>22) | (x<<10) );
break;
case 1:
temp = (uint)( (x>>6) | (x<<26) );
temp = temp ^ (uint)( (x>>11) | (x<<21) );
temp = temp ^ (uint)( (x>>25) | (x<<7) );
break;
case 2:
temp = (uint)( (x>>7) | (x<<25) );
temp = temp ^ (uint)( (x>>18) | (x<<14) );
temp = temp ^ (uint)(x>>3);
break;
case 3:
temp = (uint)( (x>>17) | (x<<15) );
temp = temp ^ (uint)( (x>>19) | (x<<13) );
temp = temp ^ (uint)(x>>10);
break;
default:
temp = x;
break;
}
return temp;
}
}
}
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