roramigator

'use strict';

/**
 * TTTTTTTTTTTTTTTTTTTTTTTHHHHHHHHH     HHHHHHHHHEEEEEEEEEEEEEEEEEEEEEE
 * T:::::::::::::::::::::TH:::::::H     H:::::::HE::::::::::::::::::::E
 * T:::::::::::::::::::::TH:::::::H     H:::::::HE::::::::::::::::::::E
 * T:::::TT:::::::TT:::::THH::::::H     H::::::HHEE::::::EEEEEEEEE::::E
 * TTTTTT  T:::::T  TTTTTT  H:::::H     H:::::H    E:::::E       EEEEEE
 *         T:::::T          H:::::H     H:::::H    E:::::E
 *         T:::::T          H::::::HHHHH::::::H    E::::::EEEEEEEEEE

ledbit

'use strict';


function writeUTF8ToBuf(str, buf, off=0) {
   for (let i=0; i < str.length; i++) {
       const charcode = str.charCodeAt(i);
       if (charcode < 0x80) buf[off++] = charcode;
       else if (charcode < 0x800) {
         buf[off++] = 0xc0 | (charcode >> 6); 
         buf[off++] = 0x80 | (charcode & 0x3f);

paulmillr

Paul Miller's explanation of endomorphism:

---

secp256k1 is Koblitz curve (e.g. Short Weierstrass curve with a=0).

Koblitz curves allow using efficiently-computable GLV endomorphism ψ:

1. GLV endomorphism ψ transforms a point: P = (x, y) ↦ ψ(P) = (β·x mod p, y)
2. GLV scalar decomposition transforms a scalar: k ≡ k₁ + k₂·λ (mod n)