[iOS]MD5加密字符串

#import <CommonCrypto/CommonDigest.h>

+ (NSString *)MD5:(NSString *)str
{
    if (str == nil)
    {
        return nil;
    }
    const char *cStr = [str UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5( cStr, strlen(cStr), result );
    return [NSString stringWithFormat:
            @"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
            result[0], result[1], result[2], result[3], result[4], result[5], result[6], result[7],
            result[8], result[9], result[10], result[11], result[12], result[13], result[14], result[15]
            ];
}

+ (NSString *)md5:(NSString *)str
{
    return [[self MD5:str] lowercaseString];
}