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// AesCfb128Decryptor.cpp
// Implements the cAesCfb128Decryptor class decrypting data using AES CFB-128
#include "Globals.h"
#include "AesCfb128Decryptor.h"
cAesCfb128Decryptor::cAesCfb128Decryptor(void) :
m_IVOffset(0),
m_IsValid(false)
{
}
cAesCfb128Decryptor::~cAesCfb128Decryptor()
{
// Clear the leftover in-memory data, so that they can't be accessed by a backdoor
memset(&m_Aes, 0, sizeof(m_Aes));
}
void cAesCfb128Decryptor::Init(const Byte a_Key[16], const Byte a_IV[16])
{
ASSERT(!IsValid()); // Cannot Init twice
memcpy(m_IV, a_IV, 16);
aes_setkey_enc(&m_Aes, a_Key, 128);
m_IsValid = true;
}
void cAesCfb128Decryptor::ProcessData(Byte * a_DecryptedOut, const Byte * a_EncryptedIn, size_t a_Length)
{
ASSERT(IsValid()); // Must Init() first
// PolarSSL doesn't support AES-CFB8, need to implement it manually:
for (size_t i = 0; i < a_Length; i++)
{
Byte Buffer[sizeof(m_IV)];
aes_crypt_ecb(&m_Aes, AES_ENCRYPT, m_IV, Buffer);
for (size_t idx = 0; idx < sizeof(m_IV) - 1; idx++)
{
m_IV[idx] = m_IV[idx + 1];
}
m_IV[sizeof(m_IV) - 1] = a_EncryptedIn[i];
a_DecryptedOut[i] = a_EncryptedIn[i] ^ Buffer[0];
}
}
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