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logicog
bd84a542ff
Add an implementation in 8051 assembler for the generation of a ChaCha20 keystream and an encryption function using the keystream in C. A test function using the example from RFC7539 is provided in chacha20_test. Keys, nonce, and block counter and the pointers to the input plaintext, its length and the output pointer are provided via a struct chacha20, which also holds the working state of the ChaCha20 algorithm
29 lines
782 B
C
29 lines
782 B
C
#ifndef _CHACHA_H_
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#define _CHACHA_H_
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#include <stdint.h>
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// In order to test, CHACHA20_TEST needs to be defined
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// #define CHACHA20_TEST
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struct chacha20_t {
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uint8_t wstate[64]; // 64 bytes written here
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uint8_t constant[16]; // 128 bit constant (4 Big-Endian u32)
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uint8_t key[32]; // 256-bit secret key (8 Big-Endian u32)
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uint8_t cnt[4]; // 32-bit block counter 1, 2.. Big Endian!
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uint8_t nonce[12]; // 96-bit nonce (3 Big-Endian u32)
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__xdata uint8_t *plaintext;
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uint16_t length;
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__xdata uint8_t *cyphertext;
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};
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// Encrypt a plaintext with ChaCha20 as per RFC7539
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void chacha20_encrypt(void) __banked;
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#ifdef CHACHA20_TEST
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// Test ChaCha20 using the example from RFC7539
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void chacha20_test(void) __banked;
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#endif
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#endif
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