Need help regarding proper string encryption decryption

I need help regarding the string encryption and decryption in java i have string having length 16 i need to encode it and also decode it but i need encoded string to be alphanumeric and symbols only that user can type from mobile and of the size same as plain text i tried Md5 and DES but MD5 is one way 开发者_如何学JAVAonly and DES encoded string is not only alphanumeric and proper symbols tried some other ways not finding proper solution.

You can convert every character of the encoded string to its hex representation. In this case the resulting string will be alphanumeric.

The Vigenère cypher can be restricted to any desired character set and has the cyphertext the same length as the plaintext. It is not as secure as a modern cypher, but has uses in low security applications. A determined attacker will be able to break Vigenère.