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92 lines
2.7 KiB
C
92 lines
2.7 KiB
C
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#ifndef _AES_H_
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#define _AES_H_
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#include <stdint.h>
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#include <stddef.h>
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// #define the macros below to 1/0 to enable/disable the mode of operation.
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//
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// CBC enables AES encryption in CBC-mode of operation.
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// CTR enables encryption in counter-mode.
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// ECB enables the basic ECB 16-byte block algorithm. All can be enabled simultaneously.
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// The #ifndef-guard allows it to be configured before #include'ing or at compile time.
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#ifndef CBC
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#define CBC 1
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#endif
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#ifndef ECB
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#define ECB 0
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#endif
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#ifndef CTR
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#define CTR 0
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#endif
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//#define AES128 1
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//#define AES192 1
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#define AES256 1
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#define AES_BLOCKLEN 16 // Block length in bytes - AES is 128b block only
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#if defined(AES256) && (AES256 == 1)
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#define AES_KEYLEN 32
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#define AES_keyExpSize 240
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#elif defined(AES192) && (AES192 == 1)
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#define AES_KEYLEN 24
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#define AES_keyExpSize 208
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#else
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#define AES_KEYLEN 16 // Key length in bytes
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#define AES_keyExpSize 176
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#endif
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struct AES_ctx
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{
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uint8_t RoundKey[AES_keyExpSize];
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#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))
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uint8_t Iv[AES_BLOCKLEN];
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#endif
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};
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void AES_init_ctx(struct AES_ctx* ctx, const uint8_t* key);
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#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))
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void AES_init_ctx_iv(struct AES_ctx* ctx, const uint8_t* key, const uint8_t* iv);
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void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv);
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#endif
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#if defined(ECB) && (ECB == 1)
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// buffer size is exactly AES_BLOCKLEN bytes;
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// you need only AES_init_ctx as IV is not used in ECB
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// NB: ECB is considered insecure for most uses
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void AES_ECB_encrypt(const struct AES_ctx* ctx, uint8_t* buf);
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void AES_ECB_decrypt(const struct AES_ctx* ctx, uint8_t* buf);
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#endif // #if defined(ECB) && (ECB == !)
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#if defined(CBC) && (CBC == 1)
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// buffer size MUST be mutile of AES_BLOCKLEN;
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// Suggest https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7 for padding scheme
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// NOTES: you need to set IV in ctx via AES_init_ctx_iv() or AES_ctx_set_iv()
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// no IV should ever be reused with the same key
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void AES_CBC_encrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
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void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
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#endif // #if defined(CBC) && (CBC == 1)
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#if defined(CTR) && (CTR == 1)
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// Same function for encrypting as for decrypting.
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// IV is incremented for every block, and used after encryption as XOR-compliment for output
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// Suggesting https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7 for padding scheme
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// NOTES: you need to set IV in ctx with AES_init_ctx_iv() or AES_ctx_set_iv()
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// no IV should ever be reused with the same key
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void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length);
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#endif // #if defined(CTR) && (CTR == 1)
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#endif // _AES_H_
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