52 lines
1.1 KiB
C
52 lines
1.1 KiB
C
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/* simple XXTEA en/decrypt utility
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*
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* BSD Licence
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*
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* btea function is from
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* <https://secure.wikimedia.org/wikipedia/en/wiki/XXTEA#Reference_code>
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*
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* (c) by Sec <sec@42.org> 6/2011
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*/
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#include <stdint.h>
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#define DELTA 0x9e3779b9
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#define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (k[(p&3)^e] ^ z)))
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void xxtea_encode(uint32_t *v, int n, uint32_t const k[4]) {
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uint32_t y, z, sum;
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unsigned p, rounds, e;
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rounds = 6 + 52/n;
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sum = 0;
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z = v[n-1];
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do {
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sum += DELTA;
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e = (sum >> 2) & 3;
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for (p=0; p<n-1; p++) {
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y = v[p+1];
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z = v[p] += MX;
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}
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y = v[0];
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z = v[n-1] += MX;
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} while (--rounds);
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}
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void xxtea_decode(uint32_t *v, int n, uint32_t const k[4]) {
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uint32_t y, z, sum;
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unsigned p, rounds, e;
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rounds = 6 + 52/n;
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sum = rounds*DELTA;
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y = v[0];
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do {
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e = (sum >> 2) & 3;
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for (p=n-1; p>0; p--) {
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z = v[p-1];
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y = v[p] -= MX;
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}
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z = v[n-1];
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y = v[0] -= MX;
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} while ((sum -= DELTA) != 0);
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}
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