366 lines
13 KiB
C
366 lines
13 KiB
C
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/* Copyright 2014, Kenneth MacKay. Licensed under the BSD 2-clause license. */
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#ifndef _UECC_H_
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#define _UECC_H_
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#include <stdint.h>
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/* Platform selection options.
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If uECC_PLATFORM is not defined, the code will try to guess it based on compiler macros.
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Possible values for uECC_PLATFORM are defined below: */
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#define uECC_arch_other 0
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#define uECC_x86 1
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#define uECC_x86_64 2
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#define uECC_arm 3
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#define uECC_arm_thumb 4
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#define uECC_arm_thumb2 5
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#define uECC_arm64 6
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#define uECC_avr 7
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/* If desired, you can define uECC_WORD_SIZE as appropriate for your platform (1, 4, or 8 bytes).
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If uECC_WORD_SIZE is not explicitly defined then it will be automatically set based on your
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platform. */
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/* Optimization level; trade speed for code size.
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Larger values produce code that is faster but larger.
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Currently supported values are 0 - 4; 0 is unusably slow for most applications.
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Optimization level 4 currently only has an effect ARM platforms where more than one
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curve is enabled. */
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#ifndef uECC_OPTIMIZATION_LEVEL
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#define uECC_OPTIMIZATION_LEVEL 2
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#endif
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/* uECC_SQUARE_FUNC - If enabled (defined as nonzero), this will cause a specific function to be
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used for (scalar) squaring instead of the generic multiplication function. This can make things
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faster somewhat faster, but increases the code size. */
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#ifndef uECC_SQUARE_FUNC
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#define uECC_SQUARE_FUNC 0
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#endif
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/* uECC_VLI_NATIVE_LITTLE_ENDIAN - If enabled (defined as nonzero), this will switch to native
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little-endian format for *all* arrays passed in and out of the public API. This includes public
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and private keys, shared secrets, signatures and message hashes.
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Using this switch reduces the amount of call stack memory used by uECC, since less intermediate
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translations are required.
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Note that this will *only* work on native little-endian processors and it will treat the uint8_t
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arrays passed into the public API as word arrays, therefore requiring the provided byte arrays
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to be word aligned on architectures that do not support unaligned accesses.
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IMPORTANT: Keys and signatures generated with uECC_VLI_NATIVE_LITTLE_ENDIAN=1 are incompatible
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with keys and signatures generated with uECC_VLI_NATIVE_LITTLE_ENDIAN=0; all parties must use
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the same endianness. */
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#ifndef uECC_VLI_NATIVE_LITTLE_ENDIAN
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#define uECC_VLI_NATIVE_LITTLE_ENDIAN 0
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#endif
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/* Curve support selection. Set to 0 to remove that curve. */
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#ifndef uECC_SUPPORTS_secp160r1
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#define uECC_SUPPORTS_secp160r1 1
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#endif
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#ifndef uECC_SUPPORTS_secp192r1
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#define uECC_SUPPORTS_secp192r1 1
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#endif
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#ifndef uECC_SUPPORTS_secp224r1
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#define uECC_SUPPORTS_secp224r1 1
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#endif
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#ifndef uECC_SUPPORTS_secp256r1
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#define uECC_SUPPORTS_secp256r1 1
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#endif
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#ifndef uECC_SUPPORTS_secp256k1
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#define uECC_SUPPORTS_secp256k1 1
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#endif
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/* Specifies whether compressed point format is supported.
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Set to 0 to disable point compression/decompression functions. */
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#ifndef uECC_SUPPORT_COMPRESSED_POINT
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#define uECC_SUPPORT_COMPRESSED_POINT 1
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#endif
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struct uECC_Curve_t;
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typedef const struct uECC_Curve_t * uECC_Curve;
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#ifdef __cplusplus
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extern "C"
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{
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#endif
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#if uECC_SUPPORTS_secp160r1
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uECC_Curve uECC_secp160r1(void);
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#endif
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#if uECC_SUPPORTS_secp192r1
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uECC_Curve uECC_secp192r1(void);
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#endif
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#if uECC_SUPPORTS_secp224r1
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uECC_Curve uECC_secp224r1(void);
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#endif
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#if uECC_SUPPORTS_secp256r1
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uECC_Curve uECC_secp256r1(void);
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#endif
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#if uECC_SUPPORTS_secp256k1
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uECC_Curve uECC_secp256k1(void);
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#endif
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/* uECC_RNG_Function type
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The RNG function should fill 'size' random bytes into 'dest'. It should return 1 if
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'dest' was filled with random data, or 0 if the random data could not be generated.
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The filled-in values should be either truly random, or from a cryptographically-secure PRNG.
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A correctly functioning RNG function must be set (using uECC_set_rng()) before calling
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uECC_make_key() or uECC_sign().
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Setting a correctly functioning RNG function improves the resistance to side-channel attacks
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for uECC_shared_secret() and uECC_sign_deterministic().
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A correct RNG function is set by default when building for Windows, Linux, or OS X.
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If you are building on another POSIX-compliant system that supports /dev/random or /dev/urandom,
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you can define uECC_POSIX to use the predefined RNG. For embedded platforms there is no predefined
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RNG function; you must provide your own.
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*/
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typedef int (*uECC_RNG_Function)(uint8_t *dest, unsigned size);
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/* uECC_set_rng() function.
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Set the function that will be used to generate random bytes. The RNG function should
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return 1 if the random data was generated, or 0 if the random data could not be generated.
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On platforms where there is no predefined RNG function (eg embedded platforms), this must
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be called before uECC_make_key() or uECC_sign() are used.
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Inputs:
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rng_function - The function that will be used to generate random bytes.
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*/
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void uECC_set_rng(uECC_RNG_Function rng_function);
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/* uECC_get_rng() function.
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Returns the function that will be used to generate random bytes.
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*/
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uECC_RNG_Function uECC_get_rng(void);
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/* uECC_curve_private_key_size() function.
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Returns the size of a private key for the curve in bytes.
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*/
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int uECC_curve_private_key_size(uECC_Curve curve);
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/* uECC_curve_public_key_size() function.
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Returns the size of a public key for the curve in bytes.
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*/
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int uECC_curve_public_key_size(uECC_Curve curve);
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/* uECC_make_key() function.
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Create a public/private key pair.
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Outputs:
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public_key - Will be filled in with the public key. Must be at least 2 * the curve size
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(in bytes) long. For example, if the curve is secp256r1, public_key must be 64
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bytes long.
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private_key - Will be filled in with the private key. Must be as long as the curve order; this
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is typically the same as the curve size, except for secp160r1. For example, if the
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curve is secp256r1, private_key must be 32 bytes long.
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For secp160r1, private_key must be 21 bytes long! Note that the first byte will
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almost always be 0 (there is about a 1 in 2^80 chance of it being non-zero).
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Returns 1 if the key pair was generated successfully, 0 if an error occurred.
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*/
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int uECC_make_key(uint8_t *public_key, uint8_t *private_key, uECC_Curve curve);
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/* uECC_shared_secret() function.
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Compute a shared secret given your secret key and someone else's public key.
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Note: It is recommended that you hash the result of uECC_shared_secret() before using it for
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symmetric encryption or HMAC.
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Inputs:
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public_key - The public key of the remote party.
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private_key - Your private key.
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Outputs:
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secret - Will be filled in with the shared secret value. Must be the same size as the
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curve size; for example, if the curve is secp256r1, secret must be 32 bytes long.
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Returns 1 if the shared secret was generated successfully, 0 if an error occurred.
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*/
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int uECC_shared_secret(const uint8_t *public_key,
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const uint8_t *private_key,
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uint8_t *secret,
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uECC_Curve curve);
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#if uECC_SUPPORT_COMPRESSED_POINT
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/* uECC_compress() function.
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Compress a public key.
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Inputs:
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public_key - The public key to compress.
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Outputs:
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compressed - Will be filled in with the compressed public key. Must be at least
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(curve size + 1) bytes long; for example, if the curve is secp256r1,
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compressed must be 33 bytes long.
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*/
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void uECC_compress(const uint8_t *public_key, uint8_t *compressed, uECC_Curve curve);
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/* uECC_decompress() function.
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Decompress a compressed public key.
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Inputs:
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compressed - The compressed public key.
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Outputs:
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public_key - Will be filled in with the decompressed public key.
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*/
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void uECC_decompress(const uint8_t *compressed, uint8_t *public_key, uECC_Curve curve);
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#endif /* uECC_SUPPORT_COMPRESSED_POINT */
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/* uECC_valid_public_key() function.
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Check to see if a public key is valid.
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Note that you are not required to check for a valid public key before using any other uECC
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functions. However, you may wish to avoid spending CPU time computing a shared secret or
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verifying a signature using an invalid public key.
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Inputs:
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public_key - The public key to check.
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Returns 1 if the public key is valid, 0 if it is invalid.
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*/
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int uECC_valid_public_key(const uint8_t *public_key, uECC_Curve curve);
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/* uECC_compute_public_key() function.
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Compute the corresponding public key for a private key.
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Inputs:
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private_key - The private key to compute the public key for
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Outputs:
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public_key - Will be filled in with the corresponding public key
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Returns 1 if the key was computed successfully, 0 if an error occurred.
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*/
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int uECC_compute_public_key(const uint8_t *private_key, uint8_t *public_key, uECC_Curve curve);
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/* uECC_sign() function.
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Generate an ECDSA signature for a given hash value.
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Usage: Compute a hash of the data you wish to sign (SHA-2 is recommended) and pass it in to
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this function along with your private key.
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Inputs:
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private_key - Your private key.
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message_hash - The hash of the message to sign.
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hash_size - The size of message_hash in bytes.
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Outputs:
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signature - Will be filled in with the signature value. Must be at least 2 * curve size long.
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For example, if the curve is secp256r1, signature must be 64 bytes long.
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Returns 1 if the signature generated successfully, 0 if an error occurred.
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*/
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int uECC_sign(const uint8_t *private_key,
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const uint8_t *message_hash,
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unsigned hash_size,
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uint8_t *signature,
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uECC_Curve curve);
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/* uECC_HashContext structure.
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This is used to pass in an arbitrary hash function to uECC_sign_deterministic().
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The structure will be used for multiple hash computations; each time a new hash
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is computed, init_hash() will be called, followed by one or more calls to
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update_hash(), and finally a call to finish_hash() to produce the resulting hash.
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The intention is that you will create a structure that includes uECC_HashContext
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followed by any hash-specific data. For example:
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typedef struct SHA256_HashContext {
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uECC_HashContext uECC;
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SHA256_CTX ctx;
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} SHA256_HashContext;
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void init_SHA256(uECC_HashContext *base) {
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SHA256_HashContext *context = (SHA256_HashContext *)base;
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SHA256_Init(&context->ctx);
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}
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void update_SHA256(uECC_HashContext *base,
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const uint8_t *message,
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unsigned message_size) {
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SHA256_HashContext *context = (SHA256_HashContext *)base;
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SHA256_Update(&context->ctx, message, message_size);
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}
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void finish_SHA256(uECC_HashContext *base, uint8_t *hash_result) {
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SHA256_HashContext *context = (SHA256_HashContext *)base;
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SHA256_Final(hash_result, &context->ctx);
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}
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... when signing ...
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{
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uint8_t tmp[32 + 32 + 64];
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SHA256_HashContext ctx = {{&init_SHA256, &update_SHA256, &finish_SHA256, 64, 32, tmp}};
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uECC_sign_deterministic(key, message_hash, &ctx.uECC, signature);
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}
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*/
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typedef struct uECC_HashContext {
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void (*init_hash)(const struct uECC_HashContext *context);
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void (*update_hash)(const struct uECC_HashContext *context,
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const uint8_t *message,
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unsigned message_size);
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void (*finish_hash)(const struct uECC_HashContext *context, uint8_t *hash_result);
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unsigned block_size; /* Hash function block size in bytes, eg 64 for SHA-256. */
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unsigned result_size; /* Hash function result size in bytes, eg 32 for SHA-256. */
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uint8_t *tmp; /* Must point to a buffer of at least (2 * result_size + block_size) bytes. */
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} uECC_HashContext;
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/* uECC_sign_deterministic() function.
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Generate an ECDSA signature for a given hash value, using a deterministic algorithm
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(see RFC 6979). You do not need to set the RNG using uECC_set_rng() before calling
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this function; however, if the RNG is defined it will improve resistance to side-channel
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attacks.
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Usage: Compute a hash of the data you wish to sign (SHA-2 is recommended) and pass it to
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this function along with your private key and a hash context. Note that the message_hash
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does not need to be computed with the same hash function used by hash_context.
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Inputs:
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private_key - Your private key.
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message_hash - The hash of the message to sign.
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hash_size - The size of message_hash in bytes.
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hash_context - A hash context to use.
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Outputs:
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signature - Will be filled in with the signature value.
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Returns 1 if the signature generated successfully, 0 if an error occurred.
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*/
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int uECC_sign_deterministic(const uint8_t *private_key,
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const uint8_t *message_hash,
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unsigned hash_size,
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const uECC_HashContext *hash_context,
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uint8_t *signature,
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uECC_Curve curve);
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/* uECC_verify() function.
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Verify an ECDSA signature.
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Usage: Compute the hash of the signed data using the same hash as the signer and
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pass it to this function along with the signer's public key and the signature values (r and s).
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Inputs:
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public_key - The signer's public key.
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message_hash - The hash of the signed data.
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hash_size - The size of message_hash in bytes.
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signature - The signature value.
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Returns 1 if the signature is valid, 0 if it is invalid.
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*/
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int uECC_verify(const uint8_t *public_key,
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const uint8_t *message_hash,
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unsigned hash_size,
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const uint8_t *signature,
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uECC_Curve curve);
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#ifdef __cplusplus
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} /* end of extern "C" */
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#endif
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#endif /* _UECC_H_ */
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