c++ - 密文长度不是 cryptopp 中 block 大小的倍数

Question

我的程序可以加密文本并将其保存在文件中，并在从文件中获取密文后解密。

但我一直收到这个错误

terminate called after throwing an instance of 'CryptoPP::InvalidCiphertext'
what(): StreamTransformationFilter: ciphertext length is not a multiple of block size

从文件中读取数据时，我得到的文件大小为密文长度，但内容大小较小，这可能是错误的。

代码:

std::string key = "0123456789abcdef";
std::string plaintext = "name macmilan age 24 ciy bonn country germany";
std::string ciphertext;
std::string decryptedtext;

CryptoPP::AES::Encryption aesEncryption((byte *)key.c_str(), CryptoPP::AES::DEFAULT_KEYLENGTH);
CryptoPP::ECB_Mode_ExternalCipher::Encryption cbcEncryption( aesEncryption);

CryptoPP::StreamTransformationFilter stfEncryptor(cbcEncryption, new CryptoPP::StringSink( ciphertext ) );
stfEncryptor.Put( reinterpret_cast<const unsigned char*>( plaintext.c_str() ), plaintext.length() + 1 );
stfEncryptor.MessageEnd();

CryptoPP::AES::Decryption aesDecryption((byte *)key.c_str(), CryptoPP::AES::DEFAULT_KEYLENGTH);
CryptoPP::ECB_Mode_ExternalCipher::Decryption cbcDecryption( aesDecryption);

std::cout << "ciphertext Text:"<<ciphertext.c_str()<<"length"<<ciphertext.length()<< std::endl;

FILE *ptr = fopen("temp.txt", "w");

if(ptr){
    fprintf(ptr, "%s",ciphertext.c_str());
    fclose(ptr);
    ptr = NULL;
}

ptr = fopen("temp.txt", "r");
if(ptr){
    fseek(ptr, 0, SEEK_END);
    size_t size = ftell(ptr);
    std::cout << "file size"<<size<< std::endl;
    char* temp = new char[size];
    rewind(ptr);
    fscanf(ptr,"%s",temp);
    ciphertext = temp;
    delete[] temp;
    ptr = NULL;
}

std::cout << "ciphertext Text:"<<ciphertext.c_str()<<"length"<<ciphertext.length() << std::endl;
try{
    CryptoPP::StreamTransformationFilter stfDecryptor(cbcDecryption, new CryptoPP::StringSink( decryptedtext ) );
    stfDecryptor.Put( reinterpret_cast<const unsigned char*>( ciphertext.c_str() ), ciphertext.size() );
    stfDecryptor.MessageEnd();
}
catch(CryptoPP::Exception &e)
{
    std::cout << "Decrypted Text:"<<e.what();

}
std::cout << "Decrypted Text: " << std::endl;
std::cout << decryptedtext;
std::cout << std::endl << std::endl;

system("pause");

return 0;

输出:

ciphertext Text:î4¬■◄vqù┼Ä╢óΣ*₧z┐É;'!ìy─ªú√@╕╡Oh∙2♠ε\→ktáäì╘aÄδ▌length48
file size48
ciphertext Text:î4¬■◄vqù┼Ä╢óΣ*₧z┐É;'!ìy─ªú√@╕╡Oh∙2♠ε\length37
Decrypted Text:StreamTransformationFilter: ciphertext length is not a multiple o
f block sizeDecrypted Text:
name macmilan ag

Answer 1

在加密过程中，可能会出现各种字符，包括 null (0)。因此，当您在文件中写入加密字符串时，您也会写入 null。当您检索加密值时，读取器获取空字符并假定该字符串已终止。所以它会更短。为了解决这个问题，你必须使用 Base64 或 MD5 之类的编码，或者打开文件并以二进制模式读取