The following will encrypt strings of up to 15 bytes in length into strings of 22 URL-safe bytes.

There is no salting and no chaining, so a lot of security is missing. Do not use this to hide any critical information. Do no use the key used here for anything else.

It is, however, as strong as any other solution in this thread, results in two fewer bytes than the other equally strong contender, and can encode arbitrary data (including nuls and spaces). 

# Encrypter

use Crypt::Blowfish ();
use MIME::Base64 qw( encode_base64 );

my $key       = ...;
my $plaintext = ...;
die("Text to encrypt must be less than 16 bytes long\n")
   if length($plaintext) >= 16;

my $cipher = Crypt::Blowfish->new($key);
my $padded_plaintext = pack('Ca15', length($plaintext), $plaintext);
my $ciphertext1 =                $cipher->encrypt(substr($plaintext, 0
+, 8));
my $ciphertext2 = $ciphertext1 ^ $cipher->encrypt(substr($plaintext, 8
+, 8));
my $ciphertext = $ciphertext1 . $ciphertext2;
my $websafe_ciphertext = substr(encode_base64($ciphertext, ''), 0, -2)
+;

[download]
# Decrypter

use Crypt::Blowfish ();
use MIME::Base64 qw( decode_base64 );

my $key                = ...;
my $websafe_ciphertext = ...;
die("Text to decrypt must be exactly 22 bytes long\n")
   if length($plaintext) != 22;

my $cipher = Crypt::Blowfish->new($key);
my $ciphertext = decode_base64($websafe_ciphertext.'==');
my $ciphertext1 = substr($plaintext, 0, 8);
my $ciphertext2 = substr($plaintext, 8, 8);
my $padded_plaintext = $cipher->decrypt(               $cyphertext1)
                     . $cipher->decrypt($ciphertext1 ^ $cyphertext2);
my $plaintext = unpack('C/a*', $padded_plaintext);

[download]

Untested.

Update: Now uses chaining.

In reply to Re: Short & Sweet Encryption? by ikegami
in thread Short & Sweet Encryption? by inblosam

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