R/math.R

In froocpu/stellaR: A 'Stellar' Client

#' Perform simple statistical calcuations
#' @description internal functions specific to the signing of transcations, including Edwards Double and Edwards Add.
#' @return bigz (big integer)
#' @references Some reference for the ed25519 algorithm: http://ed25519.cr.yp.to/
#' @note These functions were adapted from this gist by Johan Stén: https://gist.github.com/johansten/3859fb4f9a24a5b6fee5bef86a3ad91c

.inv <- function(x) {
  return(powm(x, global$q - 2, global$q))
}

.square <- function(x) {
  return (mul.bigz(x, x) %% global$q)
}

.mult <- function(x, y) {
  return(mul.bigz(x, y) %% global$q)
}

.add <- function(x, y) {
  return (add.bigz(x, y) %% global$q)
}

.edwards_add_b <- function(x, y, z) {
  B = .square(z)
  C = .mult(x, global$bx)
  D = .mult(y, global$by)
  E = .mult(global$d, .mult(C, D))
  Fa = .add(B,-E)
  G = .add(B, E)
  H = .add(C, D)
  x3 = .mult(z, .mult(Fa, .add(.mult(
    .add(x, y), .add(global$bx, global$by)
  ),-H)))
  y3 = .mult(z, .mult(G, H))
  z3 = .mult(Fa, G)
  return(c(x3, y3, z3))
}

.edwards_double <- function(x, y, z) {
  sum2 = .square(.add(x, y))
  x2 = .square(x)
  y2 = .square(y)
  z2 = .square(z)
  e = .add(x2, y2)
  Fa = .add(x2,-y2)
  j = .add(.add(z2, z2), Fa)
  x3 = .mult(.add(e,-sum2), j)
  y3 = .mult(Fa, e)
  z3 = .mult(Fa, j)
  return(c(x3, y3, z3))
}