Decrypt GPS data from a curve25519 public key — decrypt

By default, the latitude and longitude of the GPS data collected by m-Path Sense are encrypted using an asymmetric curve25519 key to provide extra protection for these highly sensitive data. This function takes a character vector and decrypts its longitude and latitude columns using the provided key.

Usage

decrypt_gps(data, key, ignore = ":")

Arguments

data: A character vector containing hexadecimal (i.e. encrypted) data.
key: A curve25519 private key.
ignore: A string with characters to ignore from data. See sodium::hex2bin().

Value

A vector of doubles of the decrypted GPS coordinates.

Parallel

This function supports parallel processing in the sense that it is able to distribute it's computation load among multiple workers. To make use of this functionality, run future::plan("multisession") before calling this function.

Examples

library(dplyr)
library(sodium)
# Create some GPS  coordinates.
data <- data.frame(
  participant_id = "12345",
  time = as.POSIXct(c(
    "2022-12-02 12:00:00",
    "2022-12-02 12:00:01",
    "2022-12-02 12:00:02"
  )),
  longitude = c("50.12345", "50.23456", "50.34567"),
  latitude = c("4.12345", "4.23456", "4.345678")
)

# Generate keypair
key <- sodium::keygen()
pub <- sodium::pubkey(key)

# Encrypt coordinates with pubkey
# You do not need to do this for m-Path Sense
# as this is already encrypted
encrypt <- function(data, pub) {
  data <- lapply(data, charToRaw)
  data <- lapply(data, function(x) sodium::simple_encrypt(x, pub))
  data <- lapply(data, sodium::bin2hex)
  data <- unlist(data)
  data
}
data$longitude <- encrypt(data$longitude, pub)
data$latitude <- encrypt(data$latitude, pub)

# Once the data has been collected, decrypt it using decrypt_gps().
data |>
  mutate(longitude = decrypt_gps(longitude, key)) |>
  mutate(latitude = decrypt_gps(latitude, key))
#>   participant_id                time longitude latitude
#> 1          12345 2022-12-02 12:00:00  50.12345 4.123450
#> 2          12345 2022-12-02 12:00:01  50.23456 4.234560
#> 3          12345 2022-12-02 12:00:02  50.34567 4.345678