Asymmetric Cryptography

Asymmetric Encryption

How can I encrypt strings using an asymmetric key?I want to encrypt short strings (credit card numbers, etc.) and save the encrypted strings into a database. When accessing the data (i.e. the web admin), he will provide a password (the decryption key).

There are DLL components (http://www.aspencrypt.com), but I can't register a DLL on the machine (hosted server).