Crypto API

The crypto API is available from the full node via websockets.

Blinding and Un-Blinding

blind

Get signed blocks.

Generates a Pedersen Commitment: *commit = blind * G + value * G2. The commitment is 33 bytes, the blinding factor is 32 bytes.

Tip: For more information about Pedersen Commitment see: Commitment Scheme

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

Parameters

• blind: Sha-256 blind factor type

• value: Positive 64-bit integer value

Return

A 33-byte Pedersen Commitment: commit = blind G + value * G2

blind_sum

Get SHA-256 blind factor type.

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

Parameters

• blinds_in: List of SHA-256 blind factor types

• non_neg: 32-bit integer value

Return

A blind factor type.

Range Proofs

range_get_info

Gets “range proof” information.

The cli_wallet includes functionality for sending blind transfers in which the values of the input and output amounts are “blinded.”

Note: In the case where a transaction produces two or more outputs, (e.g. an amount to the intended recipient plus “charge” back to the sender), a “range proof” must be supplied to prove that none of the outputs commit to a negative value.

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

Parameters

proof: List of proof’s characters

Return

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

range_proof_sign

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

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

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

Return

A list of characters as proof in proof.

Verification

verify_sum

Verifies that commits + neg_commits + excess == 0.

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)

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

Return

(Boolean) True in event of commits + neg_commits + excess == 0, otherwise false

verify_range

Verifies range proof for 33-byte Pedersen Commitment.

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

Parameters

• commit: 33-byte pedersen commitment

• proof: List of characters

Return

A structure with success, min and max values

verify_range_proof_rewind

Verifies range proof rewind for 33-byte Pedersen Commitment.

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)

Parameters

• nonce: Sha-256 blind refactor type

• commit: 33-byte pedersen commitment

• proof: List of characters

Return

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