Hello everyone,
I was wondering if I could get some feedback on a wrapper that I wrote
to simplify CBC AES. Right now the only problem that I see is that
I'm over-allocating the array on the decrypt method by a maximum of 15
bytes (AES::BLOCKSIZE-1)
This email is kinda stemming from the confusion about the initial IV values.
A little background on the usage of the class: It is used to encrypt
packet data for a game I am working on. The plaintext of the packet
gets encrypted with the Encrypt() method and then RSAES<OAEP<SHA>> is
used to encrypt the AES Key and IV which is added to the packet
header. Any comments/suggestions/criticisms would be greatly
appreciated.
#include "crypt/aes.h"
#include "crypt/modes.h"
typedef boost::shared_array<char> SHCHAR;
class CAESProvider
{
static CryptoPP::AutoSeededRandomPool m_RPool; //instantiated in .cpp
public:
struct AESResult
{
static const size_t KEYBLOCKSIZE =
CryptoPP::AES::DEFAULT_KEYLENGTH+CryptoPP::AES::BLOCKSIZE;
AESResult(const char *key,const char *iv)
{
if(key && iv)
{
memcpy(Key(),key,CryptoPP::AES::DEFAULT_KEYLENGTH);
memcpy(IV(),iv,CryptoPP::AES::BLOCKSIZE);
}
}
char KEYBLOCK[KEYBLOCKSIZE];
char *Key() { return KEYBLOCK; }
char *IV() { return KEYBLOCK+CryptoPP::AES::DEFAULT_KEYLENGTH; }
SHCHAR Data;
unsigned DataLength;
};
static unsigned GetCypherTextLength(unsigned size)
{
return size+size%CryptoPP::AES::BLOCKSIZE;
}
static AESResult Encrypt(const char* src,unsigned length)
{
AESResult result(NULL,NULL);
m_RPool.GenerateBlock((byte
*)result.Key(),CryptoPP::AES::DEFAULT_KEYLENGTH);
m_RPool.GenerateBlock((byte
*)result.IV(),CryptoPP::AES::BLOCKSIZE);
result.DataLength = GetCypherTextLength(length);
result.Data = SHCHAR(new char[result.DataLength]);
CryptoPP::AES::Encryption aesEncryption((byte *)result.Key(),
CryptoPP::AES::DEFAULT_KEYLENGTH);
CryptoPP::CBC_Mode_ExternalCipher::Encryption
cbcEncryption(aesEncryption, (byte *)result.IV());
CryptoPP::ArraySink *buffSink = new CryptoPP::ArraySink((byte
*)result.Data.get(),result.DataLength);
CryptoPP::StreamTransformationFilter
cbcFilter(cbcEncryption,buffSink);
cbcFilter.Put((byte *)src,length);
cbcFilter.MessageEnd();
_ASSERTE(buffSink->TotalPutLength() == result.DataLength);
return result;
}
static AESResult Decrypt(const char *src,unsigned length,const char
*Key,const char *IV)
{
AESResult result(NULL,NULL);
result.Data = SHCHAR(new char[length]);
CryptoPP::AES::Decryption aesDecryption((byte *)Key,
CryptoPP::AES::DEFAULT_KEYLENGTH);
CryptoPP::CBC_Mode_ExternalCipher::Decryption cbcDecryption(
aesDecryption, (byte *)IV);
CryptoPP::ArraySink *buffSink = new CryptoPP::ArraySink((byte
*)result.Data.get(),length);
CryptoPP::StreamTransformationFilter
stfDecryptor(cbcDecryption, buffSink);
stfDecryptor.Put((byte *)src,length );
stfDecryptor.MessageEnd();
result.DataLength = (unsigned)buffSink->TotalPutLength();
return result;
}
};
Thanks,
Mikhail Davidov
DigiPen '09
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the "Crypto++ Users"
Google Group.
To unsubscribe, send an email to [EMAIL PROTECTED]
More information about Crypto++ and this group is available at
http://www.cryptopp.com.
-~----------~----~----~----~------~----~------~--~---
