How to use SHA1 Encryption and Decryption algorithm?

This is algorithm. it can be "MD5" or "SHA1".

Hash algorithm used to generate password. Allowed values are: "MD5" and
"SHA1". SHA1 hashes are a bit slower, but more secure than MD5 hashes.

System.Security.Cryptography namespace is used for encryption and decryption.

Password DeriveBytes convert it to byte first

Create Decryptor and  Create Encryptor is used for password encryption and decryption.

Below is the very useful link for understanding sha1 encryption and it is explained with example.

http://www.codeproject.com/KB/security/SimpleEncryption.aspx

hope this will helpful for you