Example of how to use the new box API from PLC

plc-box-api-example.lua

local box = require "box"

-- all keys are 32 bytes long

local f = io.open("/dev/urandom")

-- generate secret keys for Alice and Bob
local sk_a = assert(f:read(32))
local sk_b = assert(f:read(32))

-- deduce the public keys
local pk_a = box.public_key(sk_a)
local pk_b = box.public_key(sk_b)

local plaintext = "Hello Bob, this is Alice!"

-- generate a random 24 bytes nonce
local nonce = f:read(24)

-- encrypt a message from Alice to Bob
local ciphertext = assert(box.box(plaintext, nonce, pk_b, sk_a))

-- there is a 16 bit MAC in front of the message
-- note you must also send the nonce with the message to allow decryption
assert(#ciphertext - #plaintext == 16)

-- Bob decrypts the message from Alice
local decrypted = assert(box.box_open(ciphertext, nonce, pk_a, sk_b))
assert(decrypted == plaintext)

f:close()