47 lines
978 B
C++
47 lines
978 B
C++
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#include "rc4.h"
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#include <iterator>
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#include "util/logging.h"
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util::RC4::RC4(uint8_t *key, size_t key_size) {
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// initialize S-BOX
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for (size_t i = 0; i < std::size(s_box); i++)
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s_box[i] = (uint8_t) i;
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// check key size
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if (!key_size)
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return;
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// KSA
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size_t j = 0;
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for (size_t i = 0; i < std::size(s_box); i++) {
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// update
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j = (j + s_box[i] + key[i % key_size]) % std::size(s_box);
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// swap
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auto tmp = s_box[i];
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s_box[i] = s_box[j];
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s_box[j] = tmp;
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}
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}
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void util::RC4::crypt(uint8_t *data, size_t size) {
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// iterate all bytes
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for (size_t pos = 0; pos < size; pos++) {
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// update
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a = (a + 1) % std::size(s_box);
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b = (b + s_box[a]) % std::size(s_box);
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// swap
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auto tmp = s_box[a];
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s_box[a] = s_box[b];
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s_box[b] = tmp;
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// crypt
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data[pos] ^= s_box[(s_box[a] + s_box[b]) % std::size(s_box)];
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}
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}
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