oc 用DES加密+base64编码后 ，得到的字符串结尾有一小段乱码，而且很难复现，哪位大神懂，求助
base64是用GTMBase64，，DES加密方法如下：
(NSString *)encryptDESUseCBCModel:(NSString *)clearText key:(NSString *)key vi:(NSString *)vi
{
NSData *data = [clearText dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];
unsigned char buffer[[data length]];
memset(buffer, 0, sizeof(char));
size_t numBytesEncrypted = 0;
const void *vinitVec = (const void *) [vi UTF8String];
CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
kCCAlgorithmDES,
kCCOptionPKCS7Padding /*| kCCOptionECBMode*/,
[key UTF8String],
kCCKeySizeDES,
vinitVec,
[data bytes],
[data length],
buffer,
100000000,
&numBytesEncrypted);
NSString* plainText = nil;
if (cryptStatus == kCCSuccess) {
NSData *dataTemp = [NSData dataWithBytes:buffer length:(NSUInteger)numBytesEncrypted];
plainText = [GTMBase64 stringByEncodingData:dataTemp];
}else{
TestLog(@"DES加密失败");
}
return plainText;
}
NSString *jsonString = [parameters JSONString];
NSString *encodeJsonString = [EncryptUtil encryptDESUseCBCModel:jsonString key:kEncryptKey vi:kEncryptVi];