如果url中含有特殊字符（如“+ =等”）就会出现的。但是在post之前对这些特殊符号做一次UTF8就可以了解决这个问题了。下面贴代码：NSString*baseStr = [imgDatabase64Encoding];

NSString *baseString = (__bridge NSString *) CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,(CFStringRef)params, NULL,CFSTR("+"),kCFStringEncodingUTF8);

- (NSString *)md5To32bit:(NSString *)input {

const char* str = [input UTF8String];

unsigned char result[CC_MD2_DIGEST_LENGTH];

CC_MD5(str, (CC_LONG)strlen(str), result);

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

for(int i = 0; I<