whenever I specify the key for the radius server it comes type 7 as such below, if I m not wrong type 7 can be decrypted easily how I can use a encryption which cannot be decrypted.
radius server ISE-SERVERS-SEC
address ipv4 10.X.X.1 auth-port 1645 acct-port 1646
key 7 121608161C0C1E012B3F
Not all passwords can be protected efficiently. While there are functions in IOS to provide good security for login-passwords and VPN-PSK, I'm not aware of a similar function for RADIUS keys.
There are still some ways to provide security for your keys:
Use type 6 password if your device supports it. Enter the following in global config and it will convert type 7 passwords to type 6