sha1算法

本文章只对sha1算法做简单的介绍和使用方法，不做其他介绍，毕竟对于大多使用者来说会用就足够了

sha1是一种安全哈希算法，也是校验算法，可用于校验文件的完整性。

sha1可处理原始报文长度不能超过2的64次方，然后SHA1生成160位（20byte）的报文摘要。SHA1算法简单而且紧凑，容易在计算机上实现。

在开发项目过程中，很多时候会使用到sha1算法，举个简单的例子：如项目需要在网络上文件传输，但文件传输过程中不能百分百确定文件不会被人篡改或者数据丢失，而sha1可以校验文件的完整性，所以在传输文件的发送方会使用sha1计算文件而生成“160位报文摘要A” ，然后将 “160位报文摘要A” 和文件发送给接收方，接收方接到文件同样使用sha1算法对文件生成 “160位报文摘要B”，最后将“160位报文摘要A”和“160位报文摘要B”做比较，如果一致则文件传输完整。至于160位报文摘要和文件怎么传输，安全性、身份确认等功能需求就不赘述了。

sha1源码如下：

sha1头文件
sha1头文件需要注意的是：宏定义中 uint8_t、uint16_t 、uint32_t 、uint64_t 需要确保在系统上是否对应的是8bit、16bit、32bit、64bit大小。因为16位系统、32位系统、64位系统对int、long占用bit位定义不同。

#ifndef __SHA1_H__
#define __SHA1_H__

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>
#include <sys/types.h>    
#include <sys/stat.h>    
#include <fcntl.h>

#define uint64_t	long long int	
#define uint32_t	unsigned  int	
#define uint16_t	unsigned short int
#define uint8_t		unsigned char

#define int_least16_t	unsigned short int


#ifndef _SHA_enum_
#define _SHA_enum_
enum
{
	shaSuccess = 0,
	shaNull,         /* Null pointer parameter */
	shaInputTooLong, /* input data too long */
	shaStateError    /* called Input after Result */
};
#endif
#define SHA1HashSize 20
/*
* This structure will hold context information for the SHA-1
* hashing operation
*/
typedef struct SHA1Context
{
	uint32_t Intermediate_Hash[SHA1HashSize/4]; /* Message Digest */
	uint32_t Length_Low; /* Message length in bits */
	uint32_t Length_High; /* Message length in bits */
	/* Index into message block array */
	int_least16_t Message_Block_Index;
	uint8_t Message_Block[64]; /* 512-bit message blocks */
	int Computed; /* Is the digest computed? */
	int Corrupted; /* Is the message digest corrupted? */
} SHA1Context;
 
/*
* Function Prototypes
*/
int SHA1Reset( SHA1Context *sha1);
int SHA1Input( SHA1Context *sha1, const uint8_t *data, unsigned int size);
int SHA1Result( SHA1Context *sha1, uint8_t Message_Digest[SHA1HashSize]);
 
#endif

sha1.c文件

#include "sha1.h"

/*
* sha1.c
*
* Description:
* This file implements the Secure Hashing Algorithm 1 as
* defined in FIPS PUB 180-1 published April 17, 1995.
*
* The SHA-1, produces a 160-bit message digest for a given
* data stream. It should take about 2**n steps to find a
* message with the same digest as a given message and
* 2**(n/2) to find any two messages with the same digest,
* when n is the digest size in bits. Therefore, this
* algorithm can serve as a means of providing a
* "fingerprint" for a message.
*
* Portability Issues:
* SHA-1 is defined in terms of 32-bit "words". This code
* uses <stdint.h> (included via "sha1.h" to define 32 and 8
* bit unsigned integer types. If your C compiler does not
* support 32 bit unsigned integers, this code is not
* appropriate.
*
* Caveats:
* SHA-1 is designed to work with messages less than 2^64 bits
* long. Although SHA-1 allows a message digest to be generated
* for messages of any number of bits less than 2^64, this
* implementation only works with messages with a length that is
* a multiple of the size of an 8-bit character.
*
*/


#ifdef __cplusplus
extern "C"
{
#endif
 
/*
* Define the SHA1 circular left shift macro
*/
#define SHA1CircularShift(bits,word) \
	(((word) << (bits)) | ((word) >> (32-(bits))))
/* Local Function Prototyptes */
void SHA1PadMessage(SHA1Context *);
void SHA1ProcessMessageBlock(SHA1Context *);
/*
* SHA1Reset
*
* Description:
* This function will initialize the SHA1Context in preparation
* for computing a new SHA1 message digest.
*
* Parameters:
* context: [in/out]
* The context to reset.
*
* Returns:
* sha Error Code.
*
*/
int SHA1Reset(SHA1Context *context)//初始化状态
{
	if (!context)
	{
		return shaNull;
	}
	context->Length_Low = 0;
	context->Length_High = 0;
	context->Message_Block_Index = 0;
	context->Intermediate_Hash[0] = 0x67452301;//取得的HASH结果（中间数据）
	context->Intermediate_Hash[1] = 0xEFCDAB89;
	context->Intermediate_Hash[2] = 0x98BADCFE;
	context->Intermediate_Hash[3] = 0x10325476;
	context->Intermediate_Hash[4] = 0xC3D2E1F0;
	context->Computed = 0;
	context->Corrupted = 0;
	return shaSuccess;
}
 
 
/*
* SHA1Result
*
* Description:
* This function will return the 160-bit message digest into the
* Message_Digest array provided by the caller.
* NOTE: The first octet of hash is stored in the 0th element,
* the last octet of hash in the 19th element.
*
* Parameters:
* context: [in/out]
* The context to use to calculate the SHA-1 hash.
* Message_Digest: [out]
* Where the digest is returned.
*
* Returns:
* sha Error Code.
*
*/
int SHA1Result( SHA1Context *context,uint8_t Message_Digest[SHA1HashSize])
{
	int i;
	if (!context || !Message_Digest)
	{
		return shaNull;
	}
	if (context->Corrupted)
	{
		return context->Corrupted;
	}
	if (!context->Computed)
	{
		SHA1PadMessage(context);
		for(i=0; i<64; ++i)
		{
			/* message may be sensitive, clear it out */
			context->Message_Block[i] = 0;
		}
		context->Length_Low = 0; /* and clear length */
		context->Length_High = 0;
		context->Computed = 1;
	}
	for(i = 0; i < SHA1HashSize; ++i)
	{
		Message_Digest[i] = context->Intermediate_Hash[i>>2]
		>> 8 * ( 3 - ( i & 0x03 ) );
	}
	return shaSuccess;
}
 
 
/*
* SHA1Input
*
* Description:
* This function accepts an array of octets as the next portion
* of the message.
*
* Parameters:
* context: [in/out]
* The SHA context to update
* message_array: [in]
* An array of characters representing the next portion of
* the message.
* length: [in]
* The length of the message in message_array
*
* Returns:
* sha Error Code.
*
*/
 
int SHA1Input( SHA1Context *context,const uint8_t *message_array,unsigned length)
{
	if (!length)
	{
		return shaSuccess;
	}
	if (!context || !message_array)
	{
		return shaNull;
	}
	if (context->Computed)
	{
		context->Corrupted = shaStateError;
		return shaStateError;
	}
	if (context->Corrupted)
	{
		return context->Corrupted;
	}
	while(length-- && !context->Corrupted)
	{
		context->Message_Block[context->Message_Block_Index++] =
			(*message_array & 0xFF);
		context->Length_Low += 8;
		if (context->Length_Low == 0)
		{
			context->Length_High++;
			if (context->Length_High == 0)
			{
				/* Message is too long */
				context->Corrupted = 1;
			}
		}
		if (context->Message_Block_Index == 64)
		{
			SHA1ProcessMessageBlock(context);
		}
		message_array++;
	}
	return shaSuccess;
}
 
/*
* SHA1ProcessMessageBlock
*
* Description:
* This function will process the next 512 bits of the message
* stored in the Message_Block array.
*
* Parameters:
* None.
*
* Returns:
* Nothing.
*
* Comments:
* Many of the variable names in this code, especially the
* single character names, were used because those were the
* names used in the publication.
*
*/
 
void SHA1ProcessMessageBlock(SHA1Context *context)
{
	const uint32_t K[] = { /* Constants defined in SHA-1 */
		0x5A827999,
		0x6ED9EBA1,
		0x8F1BBCDC,
		0xCA62C1D6
	};
	int t; /* Loop counter */
	uint32_t temp; /* Temporary word value */
	uint32_t W[80]; /* Word sequence */
	uint32_t A, B, C, D, E; /* Word buffers */
	/*
	* Initialize the first 16 words in the array W
	*/
	for(t = 0; t < 16; t++)
	{
		W[t] = context->Message_Block[t * 4] << 24;
		W[t] |= context->Message_Block[t * 4 + 1] << 16;
		W[t] |= context->Message_Block[t * 4 + 2] << 8;
		W[t] |= context->Message_Block[t * 4 + 3];
	}
	for(t = 16; t < 80; t++)
	{
		W[t] = SHA1CircularShift(1,W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16]);
	}
	A = context->Intermediate_Hash[0];
	B = context->Intermediate_Hash[1];
	C = context->Intermediate_Hash[2];
	D = context->Intermediate_Hash[3];
	E = context->Intermediate_Hash[4];
	for(t = 0; t < 20; t++)
	{
                temp = SHA1CircularShift(5,A) +
                        ((B & C) | ((~B) & D)) + E + W[t] + K[0];
		E = D;
		D = C;
		C = SHA1CircularShift(30,B);
		B = A;
		A = temp;
	}
	for(t = 20; t < 40; t++)
	{
		temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[1];
		E = D;
		D = C;
		C = SHA1CircularShift(30,B);
		B = A;
		A = temp;
	}
	for(t = 40; t < 60; t++)
	{
		temp = SHA1CircularShift(5,A) +
			((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
		E = D;
		D = C;
		C = SHA1CircularShift(30,B);
		B = A;
		A = temp;
	}
	for(t = 60; t < 80; t++)
	{
		temp = SHA1CircularShift(5,A) + (B ^ C ^ D) + E + W[t] + K[3];
		E = D;
		D = C;
		C = SHA1CircularShift(30,B);
		B = A;
		A = temp;
	}
	context->Intermediate_Hash[0] += A;
	context->Intermediate_Hash[1] += B;
	context->Intermediate_Hash[2] += C;
	context->Intermediate_Hash[3] += D;
	context->Intermediate_Hash[4] += E;
	context->Message_Block_Index = 0;
}
 
 
/*
* SHA1PadMessage
*
* Description:
* According to the standard, the message must be padded to an even
* 512 bits. The first padding bit must be a ’1’. The last 64
* bits represent the length of the original message. All bits in
* between should be 0. This function will pad the message
* according to those rules by filling the Message_Block array
* accordingly. It will also call the ProcessMessageBlock function
* provided appropriately. When it returns, it can be assumed that
* the message digest has been computed.
*
* Parameters:
* context: [in/out]
* The context to pad
* ProcessMessageBlock: [in]
* The appropriate SHA*ProcessMessageBlock function
* Returns:
* Nothing.
*
*/
 
void SHA1PadMessage(SHA1Context *context)
{
	/*
	* Check to see if the current message block is too small to hold
	* the initial padding bits and length. If so, we will pad the
	* block, process it, and then continue padding into a second
	* block.
	*/
	if (context->Message_Block_Index > 55)
	{
		context->Message_Block[context->Message_Block_Index++] = 0x80;
		while(context->Message_Block_Index < 64)
		{
			context->Message_Block[context->Message_Block_Index++] = 0;
		}
		SHA1ProcessMessageBlock(context);
		while(context->Message_Block_Index < 56)
		{
			context->Message_Block[context->Message_Block_Index++] = 0;
		}
	}
	else
	{
		context->Message_Block[context->Message_Block_Index++] = 0x80;
		while(context->Message_Block_Index < 56)
		{
			context->Message_Block[context->Message_Block_Index++] = 0;
		}
	}
 
	/*
	* Store the message length as the last 8 octets
	*/
	context->Message_Block[56] = context->Length_High >> 24;
	context->Message_Block[57] = context->Length_High >> 16;
	context->Message_Block[58] = context->Length_High >> 8;
	context->Message_Block[59] = context->Length_High;
	context->Message_Block[60] = context->Length_Low >> 24;
	context->Message_Block[61] = context->Length_Low >> 16;
	context->Message_Block[62] = context->Length_Low >> 8;
	context->Message_Block[63] = context->Length_Low;
	SHA1ProcessMessageBlock(context);
}
 
 
#ifdef __cplusplus
}
#endif

使用例程：

void sha1_test(void)
{
        unsigned char shaval[20];
        SHA1Context sha1;

        memset(shaval, 0, 20);
        memset(&sha1, 0, sizeof(sha1));    
        SHA1Reset(&sha1);
        SHA1Input(&sha1, "1234567890", strlen("1234567890"));
        SHA1Result(&sha1, shaval);

        printf("hash value :");
        for(i=0; i<20; i++)
        {
            printf("%02X", shaval[i]);
        }
        printf("\r\n");
}