rc5.cpp

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#include <cstdint>
#include <openGPMP/nt/rc5.hpp>
 
gpmp::nt::RC5::RC5(uint32_t rounds, uint32_t wordSize, uint32_t blockSize)
    : w(wordSize), r(rounds), b(blockSize) {
    init();
}
 
void gpmp::nt::RC5::init() {
    S.resize(2 * r + 2);
    S[0] = P;
    for (uint32_t i = 1; i < 2 * r + 2; ++i) {
        S[i] = S[i - 1] + Q;
    }
}
 
void gpmp::nt::RC5::encrypt(uint32_t &A, uint32_t &B) {
    A += S[0];
    B += S[1];
    for (uint32_t i = 1; i <= r; ++i) {
        A = rotl((A ^ B), B) + S[2 * i];
        B = rotl((B ^ A), A) + S[2 * i + 1];
    }
}
 
void gpmp::nt::RC5::decrypt(uint32_t &A, uint32_t &B) {
    for (uint32_t i = r; i > 0; --i) {
        B = rotr(B - S[2 * i + 1], A) ^ A;
        A = rotr(A - S[2 * i], B) ^ B;
    }
    B -= S[1];
    A -= S[0];
}
 
uint32_t gpmp::nt::RC5::rotl(uint32_t value, uint32_t shift) {
    return (value << shift) | (value >> (w - shift));
}
 
uint32_t gpmp::nt::RC5::rotr(uint32_t value, uint32_t shift) {
    return (value >> shift) | (value << (w - shift));
}