R/des.R

In JorgeRiescoDavila/somecrypto: Implements some crypto primitives for fun only

#' Data Encryption Standard
#'
#' This implementation is bugged.
#' Already deprecated block cipher. Replaced by AES.
#'
#' @param block Block to be encrypted. Given as bit stream.
#' @param key Key used to encrypt. Given as bit stream.
#' @param decrypt Indicates whether it should work in encryption or decryption mode.
#'
#' @return Encrypted block, as bit stream.
#' @export
#'
#' @examples
des <- function(block,key,decrypt=FALSE){

  #STEP1: generate subkeys
  #permuted choice 1
  pc1 = c(
    57, 49, 41, 33, 25, 17, 9,
    1,  58, 50, 42, 34, 26, 18,
    10, 2,  59, 51, 43, 35, 27,
    19, 11, 3,  60, 52, 44, 36,
    63, 55, 47, 39, 31, 23, 15,
    7,  62, 54, 46, 38, 30, 22,
    14, 6,  61, 53, 45, 37, 29,
    21, 13, 5,  28, 20, 12, 4
  )
  #permuted choice 2
  pc2 = c(
    14, 17, 11, 24, 1,  5,
    3,  28, 15, 6,  21, 10,
    23, 19, 12, 4,  26, 8,
    16, 7,  27, 20, 13, 2,
    41, 52, 31, 37, 47, 55,
    30, 40, 51, 45, 33, 48,
    44, 49, 39, 56, 34, 53,
    46, 42, 50, 36, 29, 32
  )
  #bits to leftrotate each round
  shift = c(1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1)
  #generate subkeys
  key56 <- key[pc1]
  subkey48 <- list()
  if(decrypt==TRUE){
    shift <- -shift
  }
  for(i in 1:16){
    key56a <- key56[1:28]
    key56b <- key56[29:56]
    key56a <- leftrot(key56a,shift[i])
    key56b <- leftrot(key56b,shift[i])
    key56 <- c(key56a,key56b)
    subkey48[[i]] <- key56[pc2]
  }

  #STEP2: define the main function
  feistel <- function(block32,subkey48){
    Sboxes = list(
      matrix(c(
        14,4,13,1,2,15,11,8,3,10,6,12,5,9,0,7,
        0,15,7,4,14,2,13,1,10,6,12,11,9,5,3,8,
        4,1,14,8,13,6,2,11,15,12,9,7,3,10,5,0,
        15,12,8,2,4,9,1,7,5,11,3,14,10,0,6,13
      ),nrow=4,byrow=TRUE),
      matrix(c(
        15,1,8,14,6,11,3,4,9,7,2,13,12,0,5,10,
        3,13,4,7,15,2,8,14,12,0,1,10,6,9,11,5,
        0,14,7,11,10,4,13,1,5,8,12,6,9,3,2,15,
          13,8,10,1,3,15,4,2,11,6,7,12,0,5,14,9
      ),nrow=4,byrow=TRUE),
      matrix(c(
        10,0,9,14,6,3,15,5,1,13,12,7,11,4,2,8,
        13,7,0,9,3,4,6,10,2,8,5,14,12,11,15,1,
        13,6,4,9,8,15,3,0,11,1,2,12,5,10,14,7,
        1,10,13,0,6,9,8,7,4,15,14,3,11,5,2,12
      ),nrow=4,byrow=TRUE),
      matrix(c(
        7,13,14,3,0,6,9,10,1,2,8,5,11,12,4,15,
        13,8,11,5,6,15,0,3,4,7,2,12,1,10,14,9,
        10,6,9,0,12,11,7,13,15,1,3,14,5,2,8,4,
        3,15,0,6,10,1,13,8,9,4,5,11,12,7,2,14
      ),nrow=4,byrow=TRUE),
      matrix(c(
        2,12,4,1,7,10,11,6,8,5,3,15,13,0,14,9,
        14,11,2,12,4,7,13,1,5,0,15,10,3,9,8,6,
        4,2,1,11,10,13,7,8,15,9,12,5,6,3,0,14,
        11,8,12,7,1,14,2,13,6,15,0,9,10,4,5,3
      ),nrow=4,byrow=TRUE),
      matrix(c(
        12,1,10,15,9,2,6,8,0,13,3,4,14,7,5,11,
        10,15,4,2,7,12,9,5,6,1,13,14,0,11,3,8,
        9,14,15,5,2,8,12,3,7,0,4,10,1,13,11,6,
        4,3,2,12,9,5,15,10,11,14,1,7,6,0,8,13
      ),nrow=4,byrow=TRUE),
      matrix(c(
        4,11,2,14,15,0,8,13,3,12,9,7,5,10,6,1,
        13,0,11,7,4,9,1,10,14,3,5,12,2,15,8,6,
        1,4,11,13,12,3,7,14,10,15,6,8,0,5,9,2,
        6,11,13,8,1,4,10,7,9,5,0,15,14,2,3,12
      ),nrow=4,byrow=TRUE),
      matrix(c(
        13,2,8,4,6,15,11,1,10,9,3,14,5,0,12,7,
        1,15,13,8,10,3,7,4,12,5,6,11,0,14,9,2,
        7,11,4,1,9,12,14,2,0,6,10,13,15,3,5,8,
        2,1,14,7,4,10,8,13,15,12,9,0,3,5,6,11
      ),nrow=4,byrow=TRUE)
    )
    E  = c(
      32, 1,  2,  3,  4,  5,
      4,  5,  6,  7,  8,  9,
      8,  9, 10, 11, 12, 13,
      12, 13, 14, 15, 16, 17,
      16, 17, 18, 19, 20, 21,
      20, 21, 22, 23, 24, 25,
      24, 25, 26, 27, 28, 29,
      28, 29, 30, 31, 32,  1
    )
    P = c(16,7,20,21,29,12,28,17,1,15,23,26,5,18,31,10,
          2,8,24,14,32,27,3,9,19,13,30,6,22,11,4,25)
    block48 <- block32[E]
    block48 <- xor(block48,subkey48[[i]])
    result <- numeric()
    for(i in 0:7){
      row <- sum(block48[1:6+6*i][c(1,6)]*c(2,1))+1
      col <- sum(block48[1:6+6*i][2:5]*c(8,4,2,1))+1
      result[i+1] <- Sboxes[[i+1]][row,col]
    }
    newblock <- uintToBits(sum(result*2^(7:0*4)),size=32,little=FALSE)
    newblock <- newblock[P]
    newblock
  }

  #STEP3: cipher
  i <- 7:0*8
  iniper <- c(i+2,i+4,i+6,i+8,i+1,i+3,i+5,i+7)
  i <- c(5,1,6,2,7,3,8,4)*8
  finper <- c(i-0,i-1,i-2,i-3,i-4,i-5,i-6,i-7)
  block <- block[iniper]
  blockA <- block[1:32]
  blockB <- block[33:64]
  for(i in 1:16){
    blockB <- xor(blockA,feistel(blockB,subkey48[[i]]))
    blockA <- blockB
  }
  block <- c(blockA,blockB)
  block <- block[finper]
  as.numeric(block)
}