gistfile1.txt

> ruby slugs.rb
id: 1639513188
enciphered output, string-escaped for your convenience:
"X\xD0\x97N"
slug: lt1krc
decrypted id: 1639513188
the same?
true

slugs.rb

require 'openssl'
require 'pp'

id = rand(2**32)
puts "id: #{id}"

pack_instruction = 'L'

cryptor = OpenSSL::Cipher::Cipher.new 'AES-128-CFB'

k = 'stinkyfartz12345'
# don't make the iv and the key same for the love of god
# also never change these
cryptor.key = k
cryptor.iv = k 

cryptor.encrypt

output_buffer = ''

# Q = uint64, once you get past 18446744073709551616 things you'll
# have to update your encoding
output_buffer << cryptor.update([id].pack(pack_instruction)) 
output_buffer << cryptor.final

# o is now some bits representing your encrypted integer
puts "enciphered output, string-escaped for your convenience:"
pp output_buffer

slug = output_buffer.unpack(pack_instruction).first.to_s(36)
puts "slug: #{slug}"

decryptor = OpenSSL::Cipher::Cipher.new 'AES-128-CFB'

decryptor.key = k
decryptor.iv = k

decryptor.decrypt

decrypt_buffer = ''

decrypt_buffer << decryptor.update([slug.to_i(36)].pack(pack_instruction))
decrypt_buffer << decryptor.final

decrypted_id = decrypt_buffer.unpack(pack_instruction).first

puts "decrypted id: #{decrypted_id}"
puts "the same?"
pp id == decrypted_id