Crypto API

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Blinding and Un-Blinding

blind

fc::ecc::commitment_type graphene::app::crypto_api::blind(const fc::ecc::blind_factor_type &blind, uint64_t value) const

Generates a pedersen commitment: *commit = blind * G + value * G2. The commitment is 33 bytes, the blinding factor is 32 bytes. For more information about pederson commitment check url https://en.wikipedia.org/wiki/Commitment_scheme.

Parameters:

  • blind – Sha-256 blind factor type

  • value – Positive 64-bit integer value

Returns:

A 33-byte pedersen commitment: *commit = blind * G + value * G2

blind_sum

fc::ecc::blind_factor_type graphene::app::crypto_api::blind_sum(const std::vector<blind_factor_type> &blinds_in, uint32_t non_neg) const

Get sha-256 blind factor type.

Parameters:

  • blinds_in – List of sha-256 blind factor types

  • non_neg – 32-bit integer value

Returns:

A blind factor type


Rage Proofs

range_get_info

fc::ecc::range_proof_info graphene::app::crypto_api::range_get_info(const std::vector<char> &proof) const

Gets “range proof” info. The cli_wallet includes functionality for sending blind transfers in which the values of the input and outputs amounts are “blinded.” In the case where a transaction produces two or more outputs, (e.g. an amount to the intended recipient plus “change” back to the sender), a “range proof” must be supplied to prove that none of the outputs commit to a negative value.

Parameters:

proof – List of proof’s characters

Returns:

A range proof info structure with exponent, mantissa, min and max values

range_proof_sign

std::vector<char> graphene::app::crypto_api::range_proof_sign(uint64_t min_value, const commitment_type &commit, const blind_factor_type &commit_blind, const blind_factor_type &nonce, int8_t base10_exp, uint8_t min_bits, uint64_t actual_value) const

Proves with respect to min_value the range for pedersen commitment which has the provided blinding factor and value.

Parameters:

  • min_value – Positive 64-bit integer value

  • commit – 33-byte pedersen commitment

  • commit_blind – Sha-256 blind factor type for the correct digits

  • nonce – Sha-256 blind factor type for our non-forged signatures

  • base10_exp – Exponents base 10 in range [-1 ; 18] inclusively

  • min_bits – 8-bit positive integer, must be in range [0 ; 64] inclusively

  • actual_value – 64-bit positive integer, must be greater or equal min_value

Returns:

A list of characters as proof in proof


Verification

verify_sum

bool graphene::app::crypto_api::verify_sum(const std::vector<commitment_type> &commits_in, const std::vector<commitment_type> &neg_commits_in, int64_t excess) const

Verifies that commits + neg_commits + excess == 0.

Parameters:

  • commits_in – List of 33-byte pedersen commitments

  • neg_commits_in – List of 33-byte pedersen commitments

  • excess – Sum of two list of 33-byte pedersen commitments where sums the first set and subtracts the second

Returns:

Boolean - true in event of commits + neg_commits + excess == 0, otherwise false

verify_range

verify_range_result graphene::app::crypto_api::verify_range(const fc::ecc::commitment_type &commit, const std::vector<char> &proof) const

Verifies range proof for 33-byte pedersen commitment.

Parameters:

  • commit – 33-byte pedersen commitment

  • proof – List of characters

Returns:

A structure with success, min and max values

verify_range_proof_rewind

verify_range_proof_rewind_result graphene::app::crypto_api::verify_range_proof_rewind(const blind_factor_type &nonce, const fc::ecc::commitment_type &commit, const std::vector<char> &proof) const

Verifies range proof rewind for 33-byte pedersen commitment.

Parameters:

  • nonce – Sha-256 blind refactor type

  • commit – 33-byte pedersen commitment

  • proof – List of characters

Returns:

A structure with success, min, max, value_out, blind_out and message_out values