iOS开发中MD5加密方式

将MD5的加密方式写成NSString的Category的方式，下边是.h 和 .m的实现

#import <Foundation/Foundation.h>

#import <CommonCrypto/CommonDigest.h>

@interface NSString (MD5)

- (NSString *)stringFromMD5;

@end

#import "NSString+MD5.h"

@implementation NSString (MD5)

- (NSString *)stringFromMD5

{

    if (self == nil || [self length] == 0) {

        return nil;

    }

    const char *value = [self UTF8String];

    unsigned char outputBuffer[CC_MD4_DIGEST_LENGTH];

    CC_MD5(value, strlen(value),outputBuffer);

    NSMutableString *outputString = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH*2];

    for (int i=0; i<CC_MD5_DIGEST_LENGTH; i++) {

        [outputString appendFormat:@"%02x",outputBuffer[i]];

    }

    return outputString;

}

@end