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chjj /
Created Oct 23, 2019 — forked from sipa/
Covert ECDH over secp256k1

Covert ECDH over secp256k1

If ECDH is used to establish a shared session secret for an encrypted connection, two elliptic curve points need to be transmitted (one in each direction) before encryption starts. In order to avoid being identifiable as a (specific) ECDH negotiation, ideally those two points are sent in a way that is indistinguishable from random.

This problem is easily addressed by using curves that support Elligator-style encodings: functions that encode a (subset of) elliptic curve points as sequences of bytes with no observable bias: (almost) every byte sequence corresponds to exactly one point, and the others correspond to none.

Unfortunately, no Elligator-style encoding is known for secp256k1.

chjj / .vimrc
Created Feb 12, 2019
mini vimrc
View .vimrc
" ~/.vimrc
set nocompatible
set hidden
set ruler
set visualbell
set noerrorbells
set nostartofline
View bmocha.js
#!/usr/bin/env node
/* eslint no-control-regex: "off" */
'use strict';
const assert = require('assert');
const Path = require('path');
const {
View rewrite.js
'use strict';
const path = require('path');
const fs = require('./lib/utils/fs');
async function findFiles(dir, match, ignore, files) {
const list = await fs.readdir(dir);
for (const name of list) {
if (ignore.has(name))
chjj / sweep-bcc.js
Created Aug 8, 2017
Sweep BCC from trezor multisig
View sweep-bcc.js
'use strict';
// Sweep bcc from trezor multisig.
const assert = require('assert');
const util = require('util');
const trezor = require('trezor.js-node');
const HDPublicKey = require('bcoin/lib/hd/public');
const HARDENED = 0x80000000;
View 1000-cost.json
"hash": "0000000000000000018c59d807bff651ead9f8fd6eef075ee5cffcf98bf4674c",
"height": 464208,
"size": 998109,
"txs": 684,
"inputs": 6162,
"outputs": 1362,
"inputCost": 5578086,
"outputCost": 271012,
View libsecp256k1.wast
This file has been truncated, but you can view the full file.
(type $0 (func (param i32 i32)))
(type $1 (func (param i32 i32 i32 i32 i32 i32) (result i32)))
(type $2 (func (param i32)))
(type $3 (func (result i32)))
(type $4 (func (param i32 i32 i32 i32) (result i32)))
(type $5 (func (param i32 i32 i32) (result i32)))
(type $6 (func))
(type $7 (func (param i32) (result i32)))
View fisqrt.js
// Fast inverse square root in javascript
// Example:
// > 1 / Math.sqrt(0.15625)
// 2.5298221281347035
// > Math.pow(0.15625, -0.5)
// 2.5298221281347035
// > Q_rsqrt(0.15625)
// 2.5254863388218056
View gist:358d4b1ab1a9ad3e2f9c2421db6d4794
$ node net.js
writing pub
received pub: 026c975cf8cffd1fe2109aa042e2800eb8358864bb7b4961386cb95f3d98355d97 (33)
writing greeting
received res
SingleFundingResponse {
  channelID: 0,
  channelDerivationPoint: <Buffer 02 cd c3 b5 2f 70 a6 4c eb d5 e4 0e 17 ab 8f 2b d8 c4 fe 47 bf d6 35 5b be df 3e dd 76 87 f0 fa eb>,
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