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#!/usr/bin/env sh

##
# This is script with usefull tips taken from:
#   https://github.com/mathiasbynens/dotfiles/blob/master/.osx
#
# install it:
#   curl -sL https://raw.github.com/gist/2108403/hack.sh | sh
#

Sajjon

Merry's very quick guide to elliptic curve crypto

An elliptic curve is made up of the following:

1. A field, F_p.

• What this means is all arithmetic on scalars is modulo p.
• Modern ECC have p as some large prime.
• For curve25519, p = 2^255 - 19, a prime.

2. An equation and it's parameters:

Sajjon

#!/usr/bin/python3 -O

from math import floor, log

def montgomery_ladder(x, n, op, select):
    k = floor(log(n, 2)) + 1
    x1 = x
    x2 = op(x, x)
    for i in range(k - 2, -1, -1):
        bit = 1 if n & (1 << i) else 0

Sajjon

import random

class Montgomery:

    #     B*v^2 = u^3 + A*u^2 + u

    def __init__(self, A, B, p):
        self.A = A
        self.B = B
        self.p = p

Sajjon

import Foundation

extension UnicodeScalar : ForwardIndexType {
    public func successor() -> UnicodeScalar {
        return UnicodeScalar(value + 1)
    }
}

var operatorHeads: [UnicodeScalar] = Array("=-+!*%<>&|^~?".unicodeScalars)
operatorHeads += Array("\u{00A1}" ... "\u{00A7}")

Sajjon

/// A dictionary wrapper that uses a `CaseIterable` type as its key.
/// This differs from a dictionary in two ways:
///
/// - Key-value pairs are accessed in a fixed order, which is the same
///   as the `Key`'s `allCases` property.
/// - Every possible key must have a value given, so using the key-based
///   subscript returns a non-optional value.
struct CaseMap<Key: CaseIterable & Hashable, Value> : Collection {
  typealias Index = Key.AllCases.Index

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/// Returns a binary predicate using the given key path to create an ascending order
/// for elements of type `Root`.
func ascending<Root, Value: Comparable>(_ path: KeyPath<Root, Value>) -> (Root, Root) -> Bool {
  return { $0[keyPath: path] < $1[keyPath: path] }
}

/// Returns a binary predicate using the given key path to create a descending order
/// for elements of type `Root`.
func descending<Root, Value: Comparable>(_ path: KeyPath<Root, Value>) -> (Root, Root) -> Bool {
  return { $0[keyPath: path] > $1[keyPath: path] }

Sajjon

import Darwin

@dynamicMemberLookup
struct Environment {
  subscript(dynamicMember name: String) -> String? {
    get {
      guard let value = getenv(name) else { return nil }

      return String(validatingUTF8: value)
    }