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Sbox.cc
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Sbox.cc
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#include "Sbox.h"
/*
* Builds the S-box from a given hex string.
*/
Sbox4::Sbox4(std::string hex_string)
{
// If the string is not the right length, then we can't do anything.
if (hex_string.length() != 16)
{
throw "Wrong length of hex string! Should have length 16!";
}
// We now build and populate the map from the hex string.
for (INT4BIT i = 0 ; i < 16 ; ++i)
{
INT4BIT enciphered_value = hex_decrypt(hex_string[i]);
cipher_map.insert(std::pair<INT4BIT, INT4BIT>(i, enciphered_value));
}
}
/*
* Enciphers a 32-bit plaintext.
*/
unsigned int Sbox4::encrypt32(unsigned int plaintext)
{
unsigned int ciphertext = 0x0;
for (int i = 0 ; i < 8 ; ++i)
{
// Encipher the plain text one 4-bit word at a time.
INT4BIT current_word = plaintext & 0xF;
INT4BIT enciphered_word = cipher_map[current_word];
// Push the enciphered word on to the cipher text.
ciphertext |= (enciphered_word << (i * 4));
// Bit shift the plain text to push the word off the end.
plaintext >>= 4;
}
return(ciphertext);
}
/*
* Decrypts a hex character to return the numerical value.
*/
INT4BIT Sbox4::hex_decrypt(char& hex_character)
{
std::pair<char, INT4BIT> hex_decoding_data[] = {
std::make_pair('0', 0),
std::make_pair('1', 1),
std::make_pair('2', 2),
std::make_pair('3', 3),
std::make_pair('4', 4),
std::make_pair('5', 5),
std::make_pair('6', 6),
std::make_pair('7', 7),
std::make_pair('8', 8),
std::make_pair('9', 9),
std::make_pair('A', 10),
std::make_pair('B', 11),
std::make_pair('C', 12),
std::make_pair('D', 13),
std::make_pair('E', 14),
std::make_pair('F', 15)
};
std::map<char, INT4BIT>
hex_decoder(hex_decoding_data,
hex_decoding_data +
(sizeof(hex_decoding_data) / sizeof(hex_decoding_data[0])));
return hex_decoder[hex_character];
}