c# - .NET Encryption -

what trying when user registers password gets encrypted, , encrypted password gets saved in database, , when user logs in should decrypt password compare if user entered correct password, when try decrypt gives me "bad data" exception.

please guys. here code:

protected void btnlogin_click(object sender, eventargs e) {     try     {         private cryptography crypt = new cryptography();         var registeruser = new test.model.user();         registeruser.emailaddress = txtemail.text;         registeruser.password = txtpassword.text;         //new test().getbyusername(registeruser);         new test().getbyemail(registeruser, crypt);     }     catch (exception ex)     {      } }  public void getbyemail(user user, cryptography crypt) {     try     {         var repo = new userrepository();         var test = repo.getencryptedpasswrd(user);         var o = repo.getprivatekey(user.emailaddress);         crypt.privatekey = o;         var j = repo.getpublickey(user.emailaddress);         crypt.publickey = j;         decryptpassword(test, o, crypt);      }     catch (exception ex)     {      } }  public string decryptpassword(byte [] encryptedpassword, string privatekey, cryptography cry) {     decrypted = cry.decrypt(encryptedpassword, privatekey);    //return encoding.ascii.getstring(decrypted);     return encoding.ascii.getstring(decrypted);  }  protected void btnregister_click(object sender, eventargs e) {     cryptography crypt = new cryptography();     var registeruser = new test.model.user();     registeruser.name = txtname.text;     registeruser.surname = txtsurname.text;     registeruser.emailaddress = txtemailaddress.text;     registeruser.password = txtpassword.text;     registeruser.dateregisterd = datetime.now;     new test().registeruser(registeruser, crypt.privatekey, crypt.publickey,crypt, encrypted); }  public void registeruser(user user, string privatekey, string publickey, cryptography crypt, byte[] encrypted) {     try     {         var repo = new userrepository();         byte[] plaintext = encoding.ascii.getbytes(user.password);         encrypted = crypt.encrypt(plaintext, crypt.publickey);         user.password = encoding.ascii.getstring(encrypted);         user.privatekey = crypt.privatekey;         user.publickkey = crypt.publickey;         repo.add(user);     }     catch (exception ex)     {      } } 

thanks in advance.

as said above comment should hash .

still if want encrypt example don't decrypt password . instead should encrypt password user , compare database .

you can consider simple option hash password . http://davidhayden.com/blog/dave/archive/2004/02/16/157.aspx .