multiplication_encryption.sf

#!/usr/bin/ruby

# A very simple message encryption method based on multiplication of large numbers, for messages of arbitrary length, given a secret key.

# The encryption method is secure(-ish) as long as the secret key is not reused,
# and the prime factorization of large integers remains hard on classical computers.

func sha512_prefix(data) {
    var t = data.sha512

    while (t.begins_with('0')) {
        t = t.sha512
    }

    return t
}

func create_key(secret_key) {
    sha512_prefix(secret_key) + secret_key.sha256 -> hex.next_prime
}

func encode_msg(msg) {
    sha512_prefix(msg) + msg.deflate.ascii2hex + msg.sha256 -> hex
}

func decode_msg(q) {
    q.as_hex.hex2ascii.ascii2bin.substr(512, -256).bin2ascii.inflate
}

func encrypt_msg(msg, secret_key) {

    var p = create_key(secret_key)
    var q = encode_msg(msg)

    p*q
}

func decrypt_msg(enc, secret_key) {

    var p = create_key(secret_key)
    var q = idiv(enc,p)

    decode_msg(q)
}

var secret_key = "a very secret key"

var msg = "Hello, world!"
#var msg = File(__FILE__).read(:raw)

var enc = encrypt_msg(msg, secret_key)
var dec = decrypt_msg(enc, secret_key)

say enc
say dec

assert_eq(msg, dec)

__END__
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Hello, world!