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187 lines
9.4 KiB
187 lines
9.4 KiB
9 years ago
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#ifndef _SECP256K1_RANGEPROOF_
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# define _SECP256K1_RANGEPROOF_
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# include "secp256k1.h"
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# ifdef __cplusplus
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extern "C" {
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# endif
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#include <stdint.h>
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/** Initialize a context for usage with Pedersen commitments. */
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int secp256k1_pedersen_context_initialize(secp256k1_context_t* ctx);
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/** Generate a pedersen commitment.
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* Returns 1: commitment successfully created.
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* 0: error
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* In: ctx: pointer to a context object, initialized for signing and Pedersen commitment (cannot be NULL)
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* blind: pointer to a 32-byte blinding factor (cannot be NULL)
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* value: unsigned 64-bit integer value to commit to.
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* Out: commit: pointer to a 33-byte array for the commitment (cannot be NULL)
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*
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* Blinding factors can be generated and verified in the same way as secp256k1 private keys for ECDSA.
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*/
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SECP256K1_WARN_UNUSED_RESULT int secp256k1_pedersen_commit(
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const secp256k1_context_t* ctx,
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unsigned char *commit,
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unsigned char *blind,
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uint64_t value
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Computes the sum of multiple positive and negative blinding factors.
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* Returns 1: sum successfully computed.
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* 0: error
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* In: ctx: pointer to a context object (cannot be NULL)
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* blinds: pointer to pointers to 32-byte character arrays for blinding factors. (cannot be NULL)
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* n: number of factors pointed to by blinds.
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* nneg: how many of the initial factors should be treated with a positive sign.
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* Out: blind_out: pointer to a 32-byte array for the sum (cannot be NULL)
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*/
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SECP256K1_WARN_UNUSED_RESULT int secp256k1_pedersen_blind_sum(
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const secp256k1_context_t* ctx,
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unsigned char *blind_out,
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const unsigned char * const *blinds,
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int n,
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int npositive
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Verify a tally of pedersen commitments
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* Returns 1: commitments successfully sum to zero.
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* 0: Commitments do not sum to zero or other error.
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* In: ctx: pointer to a context object, initialized for Pedersen commitment (cannot be NULL)
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* commits: pointer to pointers to 33-byte character arrays for the commitments. (cannot be NULL if pcnt is non-zero)
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* pcnt: number of commitments pointed to by commits.
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* ncommits: pointer to pointers to 33-byte character arrays for negative commitments. (cannot be NULL if ncnt is non-zero)
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* ncnt: number of commitments pointed to by ncommits.
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* excess: signed 64bit amount to add to the total to bring it to zero, can be negative.
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*
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* This computes sum(commit[0..pcnt)) - sum(ncommit[0..ncnt)) - excess*H == 0.
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*
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* A pedersen commitment is xG + vH where G and H are generators for the secp256k1 group and x is a blinding factor,
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* while v is the committed value. For a collection of commitments to sum to zero both their blinding factors and
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* values must sum to zero.
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*
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*/
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SECP256K1_WARN_UNUSED_RESULT int secp256k1_pedersen_verify_tally(
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const secp256k1_context_t* ctx,
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const unsigned char * const *commits,
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int pcnt,
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const unsigned char * const *ncommits,
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int ncnt,
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int64_t excess
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4);
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/** Initialize a context for usage with Pedersen commitments. */
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int secp256k1_rangeproof_context_initialize(secp256k1_context_t* ctx);
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/** Verify a proof that a committed value is within a range.
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* Returns 1: Value is within the range [0..2^64), the specifically proven range is in the min/max value outputs.
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* 0: Proof failed or other error.
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* In: ctx: pointer to a context object, initialized for range-proof and commitment (cannot be NULL)
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* commit: the 33-byte commitment being proved. (cannot be NULL)
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* proof: pointer to character array with the proof. (cannot be NULL)
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* plen: length of proof in bytes.
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* Out: min_value: pointer to a unsigned int64 which will be updated with the minimum value that commit could have. (cannot be NULL)
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* max_value: pointer to a unsigned int64 which will be updated with the maximum value that commit could have. (cannot be NULL)
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*/
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SECP256K1_WARN_UNUSED_RESULT int secp256k1_rangeproof_verify(
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const secp256k1_context_t* ctx,
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uint64_t *min_value,
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uint64_t *max_value,
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const unsigned char *commit,
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const unsigned char *proof,
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int plen
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
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/** Verify a range proof proof and rewind the proof to recover information sent by its author.
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* Returns 1: Value is within the range [0..2^64), the specifically proven range is in the min/max value outputs, and the value and blinding were recovered.
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* 0: Proof failed, rewind failed, or other error.
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* In: ctx: pointer to a context object, initialized for range-proof and Pedersen commitment (cannot be NULL)
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* commit: the 33-byte commitment being proved. (cannot be NULL)
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* proof: pointer to character array with the proof. (cannot be NULL)
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* plen: length of proof in bytes.
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* nonce: 32-byte secret nonce used by the prover (cannot be NULL)
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* In/Out: blind_out: storage for the 32-byte blinding factor used for the commitment
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* value_out: pointer to an unsigned int64 which has the exact value of the commitment.
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* message_out: pointer to a 4096 byte character array to receive message data from the proof author.
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* outlen: length of message data written to message_out.
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* min_value: pointer to an unsigned int64 which will be updated with the minimum value that commit could have. (cannot be NULL)
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* max_value: pointer to an unsigned int64 which will be updated with the maximum value that commit could have. (cannot be NULL)
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*/
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SECP256K1_WARN_UNUSED_RESULT int secp256k1_rangeproof_rewind(
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const secp256k1_context_t* ctx,
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unsigned char *blind_out,
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uint64_t *value_out,
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unsigned char *message_out,
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int *outlen,
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const unsigned char *nonce,
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uint64_t *min_value,
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uint64_t *max_value,
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const unsigned char *commit,
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const unsigned char *proof,
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int plen
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(6) SECP256K1_ARG_NONNULL(7) SECP256K1_ARG_NONNULL(8) SECP256K1_ARG_NONNULL(9) SECP256K1_ARG_NONNULL(10);
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/** Author a proof that a committed value is within a range.
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* Returns 1: Proof successfully created.
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* 0: Error
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* In: ctx: pointer to a context object, initialized for range-proof, signing, and Pedersen commitment (cannot be NULL)
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* proof: pointer to array to receive the proof, can be up to 5134 bytes. (cannot be NULL)
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* min_value: constructs a proof where the verifer can tell the minimum value is at least the specified amount.
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* commit: 33-byte array with the commitment being proved.
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* blind: 32-byte blinding factor used by commit.
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* nonce: 32-byte secret nonce used to initialize the proof (value can be reverse-engineered out of the proof if this secret is known.)
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* exp: Base-10 exponent. Digits below above will be made public, but the proof will be made smaller. Allowed range is -1 to 18.
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* (-1 is a special case that makes the value public. 0 is the most private.)
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* min_bits: Number of bits of the value to keep private. (0 = auto/minimal, - 64).
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* value: Actual value of the commitment.
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* In/out: plen: point to an integer with the size of the proof buffer and the size of the constructed proof.
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*
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* If min_value or exp is non-zero then the value must be on the range [0, 2^63) to prevent the proof range from spanning past 2^64.
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*
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* If exp is -1 the value is revealed by the proof (e.g. it proves that the proof is a blinding of a specific value, without revealing the blinding key.)
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*
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* This can randomly fail with probability around one in 2^100. If this happens, buy a lottery ticket and retry with a different nonce or blinding.
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*
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*/
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SECP256K1_WARN_UNUSED_RESULT int secp256k1_rangeproof_sign(
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const secp256k1_context_t* ctx,
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unsigned char *proof,
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int *plen,
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uint64_t min_value,
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const unsigned char *commit,
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const unsigned char *blind,
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const unsigned char *nonce,
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int exp,
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int min_bits,
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uint64_t value
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(6) SECP256K1_ARG_NONNULL(7);
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/** Extract some basic information from a range-proof.
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* Returns 1: Information successfully extracted.
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* 0: Decode failed.
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* In: ctx: pointer to a context object
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* proof: pointer to character array with the proof.
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* plen: length of proof in bytes.
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* Out: exp: Exponent used in the proof (-1 means the value isn't private).
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* mantissa: Number of bits covered by the proof.
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* min_value: pointer to an unsigned int64 which will be updated with the minimum value that commit could have. (cannot be NULL)
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* max_value: pointer to an unsigned int64 which will be updated with the maximum value that commit could have. (cannot be NULL)
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*/
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SECP256K1_WARN_UNUSED_RESULT int secp256k1_rangeproof_info(
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const secp256k1_context_t* ctx,
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int *exp,
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int *mantissa,
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uint64_t *min_value,
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uint64_t *max_value,
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const unsigned char *proof,
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int plen
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
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# ifdef __cplusplus
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}
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# endif
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#endif
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