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Diffstat (limited to 'include/secp256k1.h')
| -rw-r--r-- | include/secp256k1.h | 909 |
1 files changed, 0 insertions, 909 deletions
diff --git a/include/secp256k1.h b/include/secp256k1.h deleted file mode 100644 index f4053f2..0000000 --- a/include/secp256k1.h +++ /dev/null @@ -1,909 +0,0 @@ -#ifndef SECP256K1_H -#define SECP256K1_H - -#ifdef __cplusplus -extern "C" { -#endif - -#include <stddef.h> - -/** Unless explicitly stated all pointer arguments must not be NULL. - * - * The following rules specify the order of arguments in API calls: - * - * 1. Context pointers go first, followed by output arguments, combined - * output/input arguments, and finally input-only arguments. - * 2. Array lengths always immediately follow the argument whose length - * they describe, even if this violates rule 1. - * 3. Within the OUT/OUTIN/IN groups, pointers to data that is typically generated - * later go first. This means: signatures, public nonces, secret nonces, - * messages, public keys, secret keys, tweaks. - * 4. Arguments that are not data pointers go last, from more complex to less - * complex: function pointers, algorithm names, messages, void pointers, - * counts, flags, booleans. - * 5. Opaque data pointers follow the function pointer they are to be passed to. - */ - -/** Opaque data structure that holds context information - * - * The primary purpose of context objects is to store randomization data for - * enhanced protection against side-channel leakage. This protection is only - * effective if the context is randomized after its creation. See - * secp256k1_context_create for creation of contexts and - * secp256k1_context_randomize for randomization. - * - * A secondary purpose of context objects is to store pointers to callback - * functions that the library will call when certain error states arise. See - * secp256k1_context_set_error_callback as well as - * secp256k1_context_set_illegal_callback for details. Future library versions - * may use context objects for additional purposes. - * - * A constructed context can safely be used from multiple threads - * simultaneously, but API calls that take a non-const pointer to a context - * need exclusive access to it. In particular this is the case for - * secp256k1_context_destroy, secp256k1_context_preallocated_destroy, - * and secp256k1_context_randomize. - * - * Regarding randomization, either do it once at creation time (in which case - * you do not need any locking for the other calls), or use a read-write lock. - */ -typedef struct secp256k1_context_struct secp256k1_context; - -/** Opaque data structure that holds rewritable "scratch space" - * - * The purpose of this structure is to replace dynamic memory allocations, - * because we target architectures where this may not be available. It is - * essentially a resizable (within specified parameters) block of bytes, - * which is initially created either by memory allocation or TODO as a pointer - * into some fixed rewritable space. - * - * Unlike the context object, this cannot safely be shared between threads - * without additional synchronization logic. - */ -typedef struct secp256k1_scratch_space_struct secp256k1_scratch_space; - -/** Opaque data structure that holds a parsed and valid public key. - * - * The exact representation of data inside is implementation defined and not - * guaranteed to be portable between different platforms or versions. It is - * however guaranteed to be 64 bytes in size, and can be safely copied/moved. - * If you need to convert to a format suitable for storage or transmission, - * use secp256k1_ec_pubkey_serialize and secp256k1_ec_pubkey_parse. To - * compare keys, use secp256k1_ec_pubkey_cmp. - */ -typedef struct { - unsigned char data[64]; -} secp256k1_pubkey; - -/** Opaque data structured that holds a parsed ECDSA signature. - * - * The exact representation of data inside is implementation defined and not - * guaranteed to be portable between different platforms or versions. It is - * however guaranteed to be 64 bytes in size, and can be safely copied/moved. - * If you need to convert to a format suitable for storage, transmission, or - * comparison, use the secp256k1_ecdsa_signature_serialize_* and - * secp256k1_ecdsa_signature_parse_* functions. - */ -typedef struct { - unsigned char data[64]; -} secp256k1_ecdsa_signature; - -/** A pointer to a function to deterministically generate a nonce. - * - * Returns: 1 if a nonce was successfully generated. 0 will cause signing to fail. - * Out: nonce32: pointer to a 32-byte array to be filled by the function. - * In: msg32: the 32-byte message hash being verified (will not be NULL) - * key32: pointer to a 32-byte secret key (will not be NULL) - * algo16: pointer to a 16-byte array describing the signature - * algorithm (will be NULL for ECDSA for compatibility). - * data: Arbitrary data pointer that is passed through. - * attempt: how many iterations we have tried to find a nonce. - * This will almost always be 0, but different attempt values - * are required to result in a different nonce. - * - * Except for test cases, this function should compute some cryptographic hash of - * the message, the algorithm, the key and the attempt. - */ -typedef int (*secp256k1_nonce_function)( - unsigned char *nonce32, - const unsigned char *msg32, - const unsigned char *key32, - const unsigned char *algo16, - void *data, - unsigned int attempt -); - -# if !defined(SECP256K1_GNUC_PREREQ) -# if defined(__GNUC__)&&defined(__GNUC_MINOR__) -# define SECP256K1_GNUC_PREREQ(_maj,_min) \ - ((__GNUC__<<16)+__GNUC_MINOR__>=((_maj)<<16)+(_min)) -# else -# define SECP256K1_GNUC_PREREQ(_maj,_min) 0 -# endif -# endif - -/* When this header is used at build-time the SECP256K1_BUILD define needs to be set - * to correctly setup export attributes and nullness checks. This is normally done - * by secp256k1.c but to guard against this header being included before secp256k1.c - * has had a chance to set the define (e.g. via test harnesses that just includes - * secp256k1.c) we set SECP256K1_NO_BUILD when this header is processed without the - * BUILD define so this condition can be caught. - */ -#ifndef SECP256K1_BUILD -# define SECP256K1_NO_BUILD -#endif - -/* Symbol visibility. */ -#if defined(_WIN32) - /* GCC for Windows (e.g., MinGW) accepts the __declspec syntax - * for MSVC compatibility. A __declspec declaration implies (but is not - * exactly equivalent to) __attribute__ ((visibility("default"))), and so we - * actually want __declspec even on GCC, see "Microsoft Windows Function - * Attributes" in the GCC manual and the recommendations in - * https://gcc.gnu.org/wiki/Visibility. */ -# if defined(SECP256K1_BUILD) -# if defined(DLL_EXPORT) || defined(SECP256K1_DLL_EXPORT) - /* Building libsecp256k1 as a DLL. - * 1. If using Libtool, it defines DLL_EXPORT automatically. - * 2. In other cases, SECP256K1_DLL_EXPORT must be defined. */ -# define SECP256K1_API extern __declspec (dllexport) -# endif - /* The user must define SECP256K1_STATIC when consuming libsecp256k1 as a static - * library on Windows. */ -# elif !defined(SECP256K1_STATIC) - /* Consuming libsecp256k1 as a DLL. */ -# define SECP256K1_API extern __declspec (dllimport) -# endif -#endif -#ifndef SECP256K1_API -# if defined(__GNUC__) && (__GNUC__ >= 4) && defined(SECP256K1_BUILD) - /* Building libsecp256k1 on non-Windows using GCC or compatible. */ -# define SECP256K1_API extern __attribute__ ((visibility ("default"))) -# else - /* All cases not captured above. */ -# define SECP256K1_API extern -# endif -#endif - -/* Warning attributes - * NONNULL is not used if SECP256K1_BUILD is set to avoid the compiler optimizing out - * some paranoid null checks. */ -# if defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4) -# define SECP256K1_WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__)) -# else -# define SECP256K1_WARN_UNUSED_RESULT -# endif -# if !defined(SECP256K1_BUILD) && defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4) -# define SECP256K1_ARG_NONNULL(_x) __attribute__ ((__nonnull__(_x))) -# else -# define SECP256K1_ARG_NONNULL(_x) -# endif - -/* Attribute for marking functions, types, and variables as deprecated */ -#if !defined(SECP256K1_BUILD) && defined(__has_attribute) -# if __has_attribute(__deprecated__) -# define SECP256K1_DEPRECATED(_msg) __attribute__ ((__deprecated__(_msg))) -# else -# define SECP256K1_DEPRECATED(_msg) -# endif -#else -# define SECP256K1_DEPRECATED(_msg) -#endif - -/* All flags' lower 8 bits indicate what they're for. Do not use directly. */ -#define SECP256K1_FLAGS_TYPE_MASK ((1 << 8) - 1) -#define SECP256K1_FLAGS_TYPE_CONTEXT (1 << 0) -#define SECP256K1_FLAGS_TYPE_COMPRESSION (1 << 1) -/* The higher bits contain the actual data. Do not use directly. */ -#define SECP256K1_FLAGS_BIT_CONTEXT_VERIFY (1 << 8) -#define SECP256K1_FLAGS_BIT_CONTEXT_SIGN (1 << 9) -#define SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY (1 << 10) -#define SECP256K1_FLAGS_BIT_COMPRESSION (1 << 8) - -/** Context flags to pass to secp256k1_context_create, secp256k1_context_preallocated_size, and - * secp256k1_context_preallocated_create. */ -#define SECP256K1_CONTEXT_NONE (SECP256K1_FLAGS_TYPE_CONTEXT) - -/** Deprecated context flags. These flags are treated equivalent to SECP256K1_CONTEXT_NONE. */ -#define SECP256K1_CONTEXT_VERIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_VERIFY) -#define SECP256K1_CONTEXT_SIGN (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_SIGN) - -/* Testing flag. Do not use. */ -#define SECP256K1_CONTEXT_DECLASSIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY) - -/** Flag to pass to secp256k1_ec_pubkey_serialize. */ -#define SECP256K1_EC_COMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION | SECP256K1_FLAGS_BIT_COMPRESSION) -#define SECP256K1_EC_UNCOMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION) - -/** Prefix byte used to tag various encoded curvepoints for specific purposes */ -#define SECP256K1_TAG_PUBKEY_EVEN 0x02 -#define SECP256K1_TAG_PUBKEY_ODD 0x03 -#define SECP256K1_TAG_PUBKEY_UNCOMPRESSED 0x04 -#define SECP256K1_TAG_PUBKEY_HYBRID_EVEN 0x06 -#define SECP256K1_TAG_PUBKEY_HYBRID_ODD 0x07 - -/** A built-in constant secp256k1 context object with static storage duration, to be - * used in conjunction with secp256k1_selftest. - * - * This context object offers *only limited functionality* , i.e., it cannot be used - * for API functions that perform computations involving secret keys, e.g., signing - * and public key generation. If this restriction applies to a specific API function, - * it is mentioned in its documentation. See secp256k1_context_create if you need a - * full context object that supports all functionality offered by the library. - * - * It is highly recommended to call secp256k1_selftest before using this context. - */ -SECP256K1_API const secp256k1_context *secp256k1_context_static; - -/** Deprecated alias for secp256k1_context_static. */ -SECP256K1_API const secp256k1_context *secp256k1_context_no_precomp -SECP256K1_DEPRECATED("Use secp256k1_context_static instead"); - -/** Perform basic self tests (to be used in conjunction with secp256k1_context_static) - * - * This function performs self tests that detect some serious usage errors and - * similar conditions, e.g., when the library is compiled for the wrong endianness. - * This is a last resort measure to be used in production. The performed tests are - * very rudimentary and are not intended as a replacement for running the test - * binaries. - * - * It is highly recommended to call this before using secp256k1_context_static. - * It is not necessary to call this function before using a context created with - * secp256k1_context_create (or secp256k1_context_preallocated_create), which will - * take care of performing the self tests. - * - * If the tests fail, this function will call the default error handler to abort the - * program (see secp256k1_context_set_error_callback). - */ -SECP256K1_API void secp256k1_selftest(void); - - -/** Create a secp256k1 context object (in dynamically allocated memory). - * - * This function uses malloc to allocate memory. It is guaranteed that malloc is - * called at most once for every call of this function. If you need to avoid dynamic - * memory allocation entirely, see secp256k1_context_static and the functions in - * secp256k1_preallocated.h. - * - * Returns: pointer to a newly created context object. - * In: flags: Always set to SECP256K1_CONTEXT_NONE (see below). - * - * The only valid non-deprecated flag in recent library versions is - * SECP256K1_CONTEXT_NONE, which will create a context sufficient for all functionality - * offered by the library. All other (deprecated) flags will be treated as equivalent - * to the SECP256K1_CONTEXT_NONE flag. Though the flags parameter primarily exists for - * historical reasons, future versions of the library may introduce new flags. - * - * If the context is intended to be used for API functions that perform computations - * involving secret keys, e.g., signing and public key generation, then it is highly - * recommended to call secp256k1_context_randomize on the context before calling - * those API functions. This will provide enhanced protection against side-channel - * leakage, see secp256k1_context_randomize for details. - * - * Do not create a new context object for each operation, as construction and - * randomization can take non-negligible time. - */ -SECP256K1_API secp256k1_context *secp256k1_context_create( - unsigned int flags -) SECP256K1_WARN_UNUSED_RESULT; - -/** Copy a secp256k1 context object (into dynamically allocated memory). - * - * This function uses malloc to allocate memory. It is guaranteed that malloc is - * called at most once for every call of this function. If you need to avoid dynamic - * memory allocation entirely, see the functions in secp256k1_preallocated.h. - * - * Cloning secp256k1_context_static is not possible, and should not be emulated by - * the caller (e.g., using memcpy). Create a new context instead. - * - * Returns: pointer to a newly created context object. - * Args: ctx: pointer to a context to copy (not secp256k1_context_static). - */ -SECP256K1_API secp256k1_context *secp256k1_context_clone( - const secp256k1_context *ctx -) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT; - -/** Destroy a secp256k1 context object (created in dynamically allocated memory). - * - * The context pointer may not be used afterwards. - * - * The context to destroy must have been created using secp256k1_context_create - * or secp256k1_context_clone. If the context has instead been created using - * secp256k1_context_preallocated_create or secp256k1_context_preallocated_clone, the - * behaviour is undefined. In that case, secp256k1_context_preallocated_destroy must - * be used instead. - * - * Args: ctx: pointer to a context to destroy, constructed using - * secp256k1_context_create or secp256k1_context_clone - * (i.e., not secp256k1_context_static). - */ -SECP256K1_API void secp256k1_context_destroy( - secp256k1_context *ctx -) SECP256K1_ARG_NONNULL(1); - -/** Set a callback function to be called when an illegal argument is passed to - * an API call. It will only trigger for violations that are mentioned - * explicitly in the header. - * - * The philosophy is that these shouldn't be dealt with through a - * specific return value, as calling code should not have branches to deal with - * the case that this code itself is broken. - * - * On the other hand, during debug stage, one would want to be informed about - * such mistakes, and the default (crashing) may be inadvisable. - * When this callback is triggered, the API function called is guaranteed not - * to cause a crash, though its return value and output arguments are - * undefined. - * - * When this function has not been called (or called with fn==NULL), then the - * default handler will be used. The library provides a default handler which - * writes the message to stderr and calls abort. This default handler can be - * replaced at link time if the preprocessor macro - * USE_EXTERNAL_DEFAULT_CALLBACKS is defined, which is the case if the build - * has been configured with --enable-external-default-callbacks. Then the - * following two symbols must be provided to link against: - * - void secp256k1_default_illegal_callback_fn(const char *message, void *data); - * - void secp256k1_default_error_callback_fn(const char *message, void *data); - * The library can call these default handlers even before a proper callback data - * pointer could have been set using secp256k1_context_set_illegal_callback or - * secp256k1_context_set_error_callback, e.g., when the creation of a context - * fails. In this case, the corresponding default handler will be called with - * the data pointer argument set to NULL. - * - * Args: ctx: pointer to a context object. - * In: fun: pointer to a function to call when an illegal argument is - * passed to the API, taking a message and an opaque pointer. - * (NULL restores the default handler.) - * data: the opaque pointer to pass to fun above, must be NULL for the default handler. - * - * See also secp256k1_context_set_error_callback. - */ -SECP256K1_API void secp256k1_context_set_illegal_callback( - secp256k1_context *ctx, - void (*fun)(const char *message, void *data), - const void *data -) SECP256K1_ARG_NONNULL(1); - -/** Set a callback function to be called when an internal consistency check - * fails. - * - * The default callback writes an error message to stderr and calls abort - * to abort the program. - * - * This can only trigger in case of a hardware failure, miscompilation, - * memory corruption, serious bug in the library, or other error would can - * otherwise result in undefined behaviour. It will not trigger due to mere - * incorrect usage of the API (see secp256k1_context_set_illegal_callback - * for that). After this callback returns, anything may happen, including - * crashing. - * - * Args: ctx: pointer to a context object. - * In: fun: pointer to a function to call when an internal error occurs, - * taking a message and an opaque pointer (NULL restores the - * default handler, see secp256k1_context_set_illegal_callback - * for details). - * data: the opaque pointer to pass to fun above, must be NULL for the default handler. - * - * See also secp256k1_context_set_illegal_callback. - */ -SECP256K1_API void secp256k1_context_set_error_callback( - secp256k1_context *ctx, - void (*fun)(const char *message, void *data), - const void *data -) SECP256K1_ARG_NONNULL(1); - -/** Create a secp256k1 scratch space object. - * - * Returns: a newly created scratch space. - * Args: ctx: pointer to a context object. - * In: size: amount of memory to be available as scratch space. Some extra - * (<100 bytes) will be allocated for extra accounting. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT secp256k1_scratch_space *secp256k1_scratch_space_create( - const secp256k1_context *ctx, - size_t size -) SECP256K1_ARG_NONNULL(1); - -/** Destroy a secp256k1 scratch space. - * - * The pointer may not be used afterwards. - * Args: ctx: pointer to a context object. - * scratch: space to destroy - */ -SECP256K1_API void secp256k1_scratch_space_destroy( - const secp256k1_context *ctx, - secp256k1_scratch_space *scratch -) SECP256K1_ARG_NONNULL(1); - -/** Parse a variable-length public key into the pubkey object. - * - * Returns: 1 if the public key was fully valid. - * 0 if the public key could not be parsed or is invalid. - * Args: ctx: pointer to a context object. - * Out: pubkey: pointer to a pubkey object. If 1 is returned, it is set to a - * parsed version of input. If not, its value is undefined. - * In: input: pointer to a serialized public key - * inputlen: length of the array pointed to by input - * - * This function supports parsing compressed (33 bytes, header byte 0x02 or - * 0x03), uncompressed (65 bytes, header byte 0x04), or hybrid (65 bytes, header - * byte 0x06 or 0x07) format public keys. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_parse( - const secp256k1_context *ctx, - secp256k1_pubkey *pubkey, - const unsigned char *input, - size_t inputlen -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Serialize a pubkey object into a serialized byte sequence. - * - * Returns: 1 always. - * Args: ctx: pointer to a context object. - * Out: output: pointer to a 65-byte (if compressed==0) or 33-byte (if - * compressed==1) byte array to place the serialized key - * in. - * In/Out: outputlen: pointer to an integer which is initially set to the - * size of output, and is overwritten with the written - * size. - * In: pubkey: pointer to a secp256k1_pubkey containing an - * initialized public key. - * flags: SECP256K1_EC_COMPRESSED if serialization should be in - * compressed format, otherwise SECP256K1_EC_UNCOMPRESSED. - */ -SECP256K1_API int secp256k1_ec_pubkey_serialize( - const secp256k1_context *ctx, - unsigned char *output, - size_t *outputlen, - const secp256k1_pubkey *pubkey, - unsigned int flags -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); - -/** Compare two public keys using lexicographic (of compressed serialization) order - * - * Returns: <0 if the first public key is less than the second - * >0 if the first public key is greater than the second - * 0 if the two public keys are equal - * Args: ctx: pointer to a context object - * In: pubkey1: first public key to compare - * pubkey2: second public key to compare - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_cmp( - const secp256k1_context *ctx, - const secp256k1_pubkey *pubkey1, - const secp256k1_pubkey *pubkey2 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Parse an ECDSA signature in compact (64 bytes) format. - * - * Returns: 1 when the signature could be parsed, 0 otherwise. - * Args: ctx: pointer to a context object - * Out: sig: pointer to a signature object - * In: input64: pointer to the 64-byte array to parse - * - * The signature must consist of a 32-byte big endian R value, followed by a - * 32-byte big endian S value. If R or S fall outside of [0..order-1], the - * encoding is invalid. R and S with value 0 are allowed in the encoding. - * - * After the call, sig will always be initialized. If parsing failed or R or - * S are zero, the resulting sig value is guaranteed to fail verification for - * any message and public key. - */ -SECP256K1_API int secp256k1_ecdsa_signature_parse_compact( - const secp256k1_context *ctx, - secp256k1_ecdsa_signature *sig, - const unsigned char *input64 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Parse a DER ECDSA signature. - * - * Returns: 1 when the signature could be parsed, 0 otherwise. - * Args: ctx: pointer to a context object - * Out: sig: pointer to a signature object - * In: input: pointer to the signature to be parsed - * inputlen: the length of the array pointed to be input - * - * This function will accept any valid DER encoded signature, even if the - * encoded numbers are out of range. - * - * After the call, sig will always be initialized. If parsing failed or the - * encoded numbers are out of range, signature verification with it is - * guaranteed to fail for every message and public key. - */ -SECP256K1_API int secp256k1_ecdsa_signature_parse_der( - const secp256k1_context *ctx, - secp256k1_ecdsa_signature *sig, - const unsigned char *input, - size_t inputlen -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Serialize an ECDSA signature in DER format. - * - * Returns: 1 if enough space was available to serialize, 0 otherwise - * Args: ctx: pointer to a context object - * Out: output: pointer to an array to store the DER serialization - * In/Out: outputlen: pointer to a length integer. Initially, this integer - * should be set to the length of output. After the call - * it will be set to the length of the serialization (even - * if 0 was returned). - * In: sig: pointer to an initialized signature object - */ -SECP256K1_API int secp256k1_ecdsa_signature_serialize_der( - const secp256k1_context *ctx, - unsigned char *output, - size_t *outputlen, - const secp256k1_ecdsa_signature *sig -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); - -/** Serialize an ECDSA signature in compact (64 byte) format. - * - * Returns: 1 - * Args: ctx: pointer to a context object - * Out: output64: pointer to a 64-byte array to store the compact serialization - * In: sig: pointer to an initialized signature object - * - * See secp256k1_ecdsa_signature_parse_compact for details about the encoding. - */ -SECP256K1_API int secp256k1_ecdsa_signature_serialize_compact( - const secp256k1_context *ctx, - unsigned char *output64, - const secp256k1_ecdsa_signature *sig -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Verify an ECDSA signature. - * - * Returns: 1: correct signature - * 0: incorrect or unparseable signature - * Args: ctx: pointer to a context object - * In: sig: the signature being verified. - * msghash32: the 32-byte message hash being verified. - * The verifier must make sure to apply a cryptographic - * hash function to the message by itself and not accept an - * msghash32 value directly. Otherwise, it would be easy to - * create a "valid" signature without knowledge of the - * secret key. See also - * https://bitcoin.stackexchange.com/a/81116/35586 for more - * background on this topic. - * pubkey: pointer to an initialized public key to verify with. - * - * To avoid accepting malleable signatures, only ECDSA signatures in lower-S - * form are accepted. - * - * If you need to accept ECDSA signatures from sources that do not obey this - * rule, apply secp256k1_ecdsa_signature_normalize to the signature prior to - * verification, but be aware that doing so results in malleable signatures. - * - * For details, see the comments for that function. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_verify( - const secp256k1_context *ctx, - const secp256k1_ecdsa_signature *sig, - const unsigned char *msghash32, - const secp256k1_pubkey *pubkey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); - -/** Convert a signature to a normalized lower-S form. - * - * Returns: 1 if sigin was not normalized, 0 if it already was. - * Args: ctx: pointer to a context object - * Out: sigout: pointer to a signature to fill with the normalized form, - * or copy if the input was already normalized. (can be NULL if - * you're only interested in whether the input was already - * normalized). - * In: sigin: pointer to a signature to check/normalize (can be identical to sigout) - * - * With ECDSA a third-party can forge a second distinct signature of the same - * message, given a single initial signature, but without knowing the key. This - * is done by negating the S value modulo the order of the curve, 'flipping' - * the sign of the random point R which is not included in the signature. - * - * Forgery of the same message isn't universally problematic, but in systems - * where message malleability or uniqueness of signatures is important this can - * cause issues. This forgery can be blocked by all verifiers forcing signers - * to use a normalized form. - * - * The lower-S form reduces the size of signatures slightly on average when - * variable length encodings (such as DER) are used and is cheap to verify, - * making it a good choice. Security of always using lower-S is assured because - * anyone can trivially modify a signature after the fact to enforce this - * property anyway. - * - * The lower S value is always between 0x1 and - * 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0, - * inclusive. - * - * No other forms of ECDSA malleability are known and none seem likely, but - * there is no formal proof that ECDSA, even with this additional restriction, - * is free of other malleability. Commonly used serialization schemes will also - * accept various non-unique encodings, so care should be taken when this - * property is required for an application. - * - * The secp256k1_ecdsa_sign function will by default create signatures in the - * lower-S form, and secp256k1_ecdsa_verify will not accept others. In case - * signatures come from a system that cannot enforce this property, - * secp256k1_ecdsa_signature_normalize must be called before verification. - */ -SECP256K1_API int secp256k1_ecdsa_signature_normalize( - const secp256k1_context *ctx, - secp256k1_ecdsa_signature *sigout, - const secp256k1_ecdsa_signature *sigin -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3); - -/** An implementation of RFC6979 (using HMAC-SHA256) as nonce generation function. - * If a data pointer is passed, it is assumed to be a pointer to 32 bytes of - * extra entropy. - */ -SECP256K1_API const secp256k1_nonce_function secp256k1_nonce_function_rfc6979; - -/** A default safe nonce generation function (currently equal to secp256k1_nonce_function_rfc6979). */ -SECP256K1_API const secp256k1_nonce_function secp256k1_nonce_function_default; - -/** Create an ECDSA signature. - * - * Returns: 1: signature created - * 0: the nonce generation function failed, or the secret key was invalid. - * Args: ctx: pointer to a context object (not secp256k1_context_static). - * Out: sig: pointer to an array where the signature will be placed. - * In: msghash32: the 32-byte message hash being signed. - * seckey: pointer to a 32-byte secret key. - * noncefp: pointer to a nonce generation function. If NULL, - * secp256k1_nonce_function_default is used. - * ndata: pointer to arbitrary data used by the nonce generation function - * (can be NULL). If it is non-NULL and - * secp256k1_nonce_function_default is used, then ndata must be a - * pointer to 32-bytes of additional data. - * - * The created signature is always in lower-S form. See - * secp256k1_ecdsa_signature_normalize for more details. - */ -SECP256K1_API int secp256k1_ecdsa_sign( - const secp256k1_context *ctx, - secp256k1_ecdsa_signature *sig, - const unsigned char *msghash32, - const unsigned char *seckey, - secp256k1_nonce_function noncefp, - const void *ndata -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); - -/** Verify an ECDSA secret key. - * - * A secret key is valid if it is not 0 and less than the secp256k1 curve order - * when interpreted as an integer (most significant byte first). The - * probability of choosing a 32-byte string uniformly at random which is an - * invalid secret key is negligible. - * - * Returns: 1: secret key is valid - * 0: secret key is invalid - * Args: ctx: pointer to a context object. - * In: seckey: pointer to a 32-byte secret key. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_verify( - const secp256k1_context *ctx, - const unsigned char *seckey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); - -/** Compute the public key for a secret key. - * - * Returns: 1: secret was valid, public key stores. - * 0: secret was invalid, try again. - * Args: ctx: pointer to a context object (not secp256k1_context_static). - * Out: pubkey: pointer to the created public key. - * In: seckey: pointer to a 32-byte secret key. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create( - const secp256k1_context *ctx, - secp256k1_pubkey *pubkey, - const unsigned char *seckey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Negates a secret key in place. - * - * Returns: 0 if the given secret key is invalid according to - * secp256k1_ec_seckey_verify. 1 otherwise - * Args: ctx: pointer to a context object - * In/Out: seckey: pointer to the 32-byte secret key to be negated. If the - * secret key is invalid according to - * secp256k1_ec_seckey_verify, this function returns 0 and - * seckey will be set to some unspecified value. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_negate( - const secp256k1_context *ctx, - unsigned char *seckey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); - -/** Same as secp256k1_ec_seckey_negate, but DEPRECATED. Will be removed in - * future versions. */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_negate( - const secp256k1_context *ctx, - unsigned char *seckey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) - SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_negate instead"); - -/** Negates a public key in place. - * - * Returns: 1 always - * Args: ctx: pointer to a context object - * In/Out: pubkey: pointer to the public key to be negated. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_negate( - const secp256k1_context *ctx, - secp256k1_pubkey *pubkey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2); - -/** Tweak a secret key by adding tweak to it. - * - * Returns: 0 if the arguments are invalid or the resulting secret key would be - * invalid (only when the tweak is the negation of the secret key). 1 - * otherwise. - * Args: ctx: pointer to a context object. - * In/Out: seckey: pointer to a 32-byte secret key. If the secret key is - * invalid according to secp256k1_ec_seckey_verify, this - * function returns 0. seckey will be set to some unspecified - * value if this function returns 0. - * In: tweak32: pointer to a 32-byte tweak, which must be valid according to - * secp256k1_ec_seckey_verify or 32 zero bytes. For uniformly - * random 32-byte tweaks, the chance of being invalid is - * negligible (around 1 in 2^128). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_add( - const secp256k1_context *ctx, - unsigned char *seckey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Same as secp256k1_ec_seckey_tweak_add, but DEPRECATED. Will be removed in - * future versions. */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add( - const secp256k1_context *ctx, - unsigned char *seckey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) - SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_add instead"); - -/** Tweak a public key by adding tweak times the generator to it. - * - * Returns: 0 if the arguments are invalid or the resulting public key would be - * invalid (only when the tweak is the negation of the corresponding - * secret key). 1 otherwise. - * Args: ctx: pointer to a context object. - * In/Out: pubkey: pointer to a public key object. pubkey will be set to an - * invalid value if this function returns 0. - * In: tweak32: pointer to a 32-byte tweak, which must be valid according to - * secp256k1_ec_seckey_verify or 32 zero bytes. For uniformly - * random 32-byte tweaks, the chance of being invalid is - * negligible (around 1 in 2^128). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add( - const secp256k1_context *ctx, - secp256k1_pubkey *pubkey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Tweak a secret key by multiplying it by a tweak. - * - * Returns: 0 if the arguments are invalid. 1 otherwise. - * Args: ctx: pointer to a context object. - * In/Out: seckey: pointer to a 32-byte secret key. If the secret key is - * invalid according to secp256k1_ec_seckey_verify, this - * function returns 0. seckey will be set to some unspecified - * value if this function returns 0. - * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to - * secp256k1_ec_seckey_verify, this function returns 0. For - * uniformly random 32-byte arrays the chance of being invalid - * is negligible (around 1 in 2^128). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_mul( - const secp256k1_context *ctx, - unsigned char *seckey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Same as secp256k1_ec_seckey_tweak_mul, but DEPRECATED. Will be removed in - * future versions. */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul( - const secp256k1_context *ctx, - unsigned char *seckey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) - SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_mul instead"); - -/** Tweak a public key by multiplying it by a tweak value. - * - * Returns: 0 if the arguments are invalid. 1 otherwise. - * Args: ctx: pointer to a context object. - * In/Out: pubkey: pointer to a public key object. pubkey will be set to an - * invalid value if this function returns 0. - * In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to - * secp256k1_ec_seckey_verify, this function returns 0. For - * uniformly random 32-byte arrays the chance of being invalid - * is negligible (around 1 in 2^128). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul( - const secp256k1_context *ctx, - secp256k1_pubkey *pubkey, - const unsigned char *tweak32 -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Randomizes the context to provide enhanced protection against side-channel leakage. - * - * Returns: 1: randomization successful - * 0: error - * Args: ctx: pointer to a context object (not secp256k1_context_static). - * In: seed32: pointer to a 32-byte random seed (NULL resets to initial state). - * - * While secp256k1 code is written and tested to be constant-time no matter what - * secret values are, it is possible that a compiler may output code which is not, - * and also that the CPU may not emit the same radio frequencies or draw the same - * amount of power for all values. Randomization of the context shields against - * side-channel observations which aim to exploit secret-dependent behaviour in - * certain computations which involve secret keys. - * - * It is highly recommended to call this function on contexts returned from - * secp256k1_context_create or secp256k1_context_clone (or from the corresponding - * functions in secp256k1_preallocated.h) before using these contexts to call API - * functions that perform computations involving secret keys, e.g., signing and - * public key generation. It is possible to call this function more than once on - * the same context, and doing so before every few computations involving secret - * keys is recommended as a defense-in-depth measure. Randomization of the static - * context secp256k1_context_static is not supported. - * - * Currently, the random seed is mainly used for blinding multiplications of a - * secret scalar with the elliptic curve base point. Multiplications of this - * kind are performed by exactly those API functions which are documented to - * require a context that is not secp256k1_context_static. As a rule of thumb, - * these are all functions which take a secret key (or a keypair) as an input. - * A notable exception to that rule is the ECDH module, which relies on a different - * kind of elliptic curve point multiplication and thus does not benefit from - * enhanced protection against side-channel leakage currently. - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_context_randomize( - secp256k1_context *ctx, - const unsigned char *seed32 -) SECP256K1_ARG_NONNULL(1); - -/** Add a number of public keys together. - * - * Returns: 1: the sum of the public keys is valid. - * 0: the sum of the public keys is not valid. - * Args: ctx: pointer to a context object. - * Out: out: pointer to a public key object for placing the resulting public key. - * In: ins: pointer to array of pointers to public keys. - * n: the number of public keys to add together (must be at least 1). - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_combine( - const secp256k1_context *ctx, - secp256k1_pubkey *out, - const secp256k1_pubkey * const *ins, - size_t n -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3); - -/** Compute a tagged hash as defined in BIP-340. - * - * This is useful for creating a message hash and achieving domain separation - * through an application-specific tag. This function returns - * SHA256(SHA256(tag)||SHA256(tag)||msg). Therefore, tagged hash - * implementations optimized for a specific tag can precompute the SHA256 state - * after hashing the tag hashes. - * - * Returns: 1 always. - * Args: ctx: pointer to a context object - * Out: hash32: pointer to a 32-byte array to store the resulting hash - * In: tag: pointer to an array containing the tag - * taglen: length of the tag array - * msg: pointer to an array containing the message - * msglen: length of the message array - */ -SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_tagged_sha256( - const secp256k1_context *ctx, - unsigned char *hash32, - const unsigned char *tag, - size_t taglen, - const unsigned char *msg, - size_t msglen -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5); - -#ifdef __cplusplus -} -#endif - -#endif /* SECP256K1_H */ |