Function secp256k1_zkp_sys::secp256k1_pedersen_blind_generator_blind_sum

pub unsafe extern "C" fn secp256k1_pedersen_blind_generator_blind_sum(
    ctx: *const Context,
    value: *const u64,
    generator_blind: *const *const c_uchar,
    blinding_factor: *const *mut c_uchar,
    n_total: size_t,
    n_inputs: size_t
) -> c_int

Sets the final Pedersen blinding factor correctly when the generators themselves have blinding factors.

Consider a generator of the form A’ = A + rG, where A is the “real” generator but A’ is the generator provided to verifiers. Then a Pedersen commitment P = vA’ + r’G really has the form vA + (vr + r’)G. To get all these (vr + r’) to sum to zero for multiple commitments, we take three arrays consisting of the vs, rs, and r's, respectively called values, generator_blinds and blinding_factors, and sum them.

The function then subtracts the sum of all (vr + r’) from the last element of the blinding_factor array, setting the total sum to zero.

Returns 1: Blinding factor successfully computed. 0: Error. A blinding_factor or generator_blind are larger than the group order (probability for random 32 byte number < 2^-127). Retry with different values.

In: ctx: pointer to a context object value: array of asset values, v in the above paragraph. May not be NULL unless n_total is 0. generator_blind: array of asset blinding factors, r in the above paragraph May not be NULL unless n_total is 0. n_total: Total size of the above arrays n_inputs: How many of the initial array elements represent commitments that will be negated in the final sum In/Out: blinding_factor: array of commitment blinding factors, r' in the above paragraph May not be NULL unless n_total is 0. the last value will be modified to get the total sum to zero.