From: Heesob Park <phasis@...>
Date: 2012-12-20T19:13:31+09:00
Subject: Re: Efficient way to encode a string with a secret string and recover it

Hi,

2012/12/20 Iñaki Baz Castillo <ibc@aliax.net>:
> Hi, basically I receive a string generated by a user, then "encode" it
> using some secret string I own and pass the result to other user, and
> when I receive such a resulting string I must be able to decode it
> using my secret string (but no other should be able to decode the
> resulting string without knowing my secret key. This is:
>
>
> original_string = "test"
>
> secret_key = "ABCD"
>
> modified_string = HASH_FUNCTION(original_string, secret_key)
>
> original_string = UNHASH_FUNCTION(modified_string, secret_key)
>
>
> Any suggestion for the above HASH_FUNCTION and UNHASH_FUNCTION? I
> would like it to be something really efficient.
>
> Thanks a lot.
>
You can use openssl module something like this:

def encrypt(input,key)
	require 'openssl'
	des = OpenSSL::Cipher::Cipher.new("des-ede-cbc")
	des.encrypt
	des.key= "%16s" % key
	des.update(input)+des.final
end

def decrypt(input,key)
	require 'openssl'
	des = OpenSSL::Cipher::Cipher.new("des-ede-cbc")
	des.decrypt
	des.key = "%16s" % key
	des.update(input)+des.final
end

But, I am not sure it is really efficient.

Regards,

Park Heesob