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31 lines
999 B
C
31 lines
999 B
C
#ifndef OBFUSCATE_H
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#define OBFUSCATE_H
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#include <stdint.h>
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/* Payload uses lower 40 bits; upper 24 bits hold verification tag. */
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#define OBF_PAYLOAD_BITS 40u
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#define OBF_PAYLOAD_MASK ((1ULL << OBF_PAYLOAD_BITS) - 1ULL)
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/* Return codes */
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#define OBF_OK 0
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#define OBF_ERR_NULL -1 /* out pointer is NULL */
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#define OBF_ERR_RANGE -2 /* val exceeds encodable payload width */
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#define OBF_ERR_VERIFY -3 /* tag mismatch (wrong seed or corrupted data) */
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/*
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* Encode uint64_t payload (e.g. flag bits) using seed-derived keystream.
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* seed is typically unix time in whole seconds shared by encoder and decoder.
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*
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* On success writes single uint64_t to *out and returns OBF_OK.
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*/
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int32_t encode(uint64_t val, uint64_t seed, uint64_t *out);
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/*
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* Decode and verify. seed must match the value used at encode time.
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* On success writes recovered payload to *out and returns OBF_OK.
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*/
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int32_t decode(uint64_t encoded_val, uint64_t seed, uint64_t *out);
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#endif /* OBFUSCATE_H */
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