MD5.h

#import <Foundation/Foundation.h>

@interface MD5 : NSObject

/**
 *	@brief	calculate a message-digest fingerprint for a input string.
 *
 *	@return	return a message-digest fingerprint
 */
+ (NSString *)MD5String:(NSString *)string;
+ (NSString *)MD5Data:(NSData *)data;  //获取某个文件（文件先转为 NSData）的 MD5值 

@end

md5.m

#import "MD5.h"
#import <CommonCrypto/CommonDigest.h>

@implementation MD5

+ (NSString *)MD5String:(NSString *)string
{
    if (string == nil || [string length] == 0) {
        return nil;
    }

    const char *value = [string UTF8String];

    unsigned char outputBuffer[CC_MD5_DIGEST_LENGTH];
    CC_MD5(value, strlen(value), outputBuffer);

    NSMutableString *outputString = [[NSMutableString alloc] initWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for (NSInteger count = 0; count < CC_MD5_DIGEST_LENGTH; count++) {
        [outputString appendFormat:@"%02x",outputBuffer[count]];
    }

    return outputString;
}

+ (NSString *)MD5Data:(NSData *)data
{
    if (data == nil || [data length] == 0) {
        return nil;
    }
    
    unsigned char outputBuffer[CC_MD5_DIGEST_LENGTH];
    CC_MD5([data bytes], [data length], outputBuffer);
    
    NSMutableString *outputString = [[NSMutableString alloc] initWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for (NSInteger count = 0; count < CC_MD5_DIGEST_LENGTH; count++) {
        [outputString appendFormat:@"%02x",outputBuffer[count]];
    }
    
    return outputString;
}

@end