R/save.R

In iamtrask/R-Homomorphic-Encryption-Package: Fully Homomorphic Encryption

#' 
#' Save and load keys and ciphertexts
#' 
#' Use these functions rather than the base R functions for saving and loading
#' of ciphertexts and keys.  Note that this is due to a limitation in Rcpp, 
#' so the \code{save}, \code{save.image} and \code{saveRDS} base R functions are
#' overriden to warn if they are used incorrectly on ciper text objects.
#' 
#' These functions provide a way to save ciphertexts and keys generated by this 
#' package to a file in such a way that they can later be restored to another
#' R session (possibly on a different machine).
#' 
#' At present no compression is performed so for long-term storage or transmission
#' over a network it would be advisable to gzip the files after creation.
#' 
#' @aliases save save.image saveRDS
#' 
#' @param object the ciphertext or keys to be saved
#' 
#' @param file the filename to save (load) the object to (from)
#' 
#' @examples
#' p <- pars("FandV")
#' keys <- keygen(p)
#' ct1 <- enc(keys$pk, 2)
#' \dontrun{saveFHE(ct1, "~/myCipherText.fhe")}
#' 
#' # Start a new session or transfer to another machine
#' \dontrun{ct1 <- loadFHE("~/myCipherText.fhe")}
saveFHE <- function(object, file) {
  if(is.null(attr(object, "FHEt")) || is.null(attr(object, "FHEs"))) stop("This function is only for saving ciphertext and key objects produced by this package.")
  file <- path.expand(file)
  UseMethod("saveFHE", object)
}

#' @rdname saveFHE
loadFHE <- function(file) {
  header <- readLines(file, n=2)
  if(header[1] != "=> FHE pkg obj <=") {
    stop("File does not contain a ciphertext or key object")
  }
  file <- path.expand(file)
  eval(parse(text=paste("loadFHE.", header[2], "(file)", sep="")))
}


##### Override built-in save functions #####

save <- function(...) {
  # Check directly specified arguments
  args <- list(...)
  for(arg in args) {
    if(!is.null(attr(arg, "FHEs")) && !is.null(attr(arg, "FHEt"))) {
      stop("Due to a limitation in Rcpp the save method cannot be used with ciphertexts.  Please use saveFHE and loadFHE instead (see ?saveFHE).")
    }
  }
  # Check variables named via list
  for(var in args$list) {
    var2 <- get(var, envir=.GlobalEnv)
    if(!is.null(attr(var2, "FHEs")) && !is.null(attr(var2, "FHEt"))) {
      stop("Due to a limitation in Rcpp the save method cannot be used with ciphertexts.  Please use saveFHE and loadFHE instead (see ?saveFHE).")
    }
  }
  
  base::save(...)
}

save.image <- function(...) {
  vars <- ls(all.names=TRUE, envir=.GlobalEnv)
  nonCT <- c()
  for(var in vars) {
    var2 <- get(var, envir=.GlobalEnv)
    if(!is.null(attr(var2, "FHEs")) && !is.null(attr(var2, "FHEt"))) {
      warning(var, " not being saved in image - all encryption variables omitted.")
    } else {
      nonCT <- c(nonCT, var)
    }
  }
  
  args <- list(...)
  if(is.null(args$file)) {
    base::save(list=nonCT, file=".RData", envir=.GlobalEnv, ...)
  } else {
    base::save(list=nonCT, envir=.GlobalEnv, ...)
  }
}

saveRDS <- function(object, ...) {
  if(!is.null(attr(object, "FHEs")) && !is.null(attr(object, "FHEt"))) {
    stop("Due to a limitation in Rcpp the saveRDS method cannot be used with ciphertexts.  Please use saveFHE and loadFHE instead (see ?saveFHE).")
  }
  
  base::saveRDS(object, ...)
}