secret key

when somebody take my computer, he can export easyly my secret key.After he can easily encrypt message witout my autorisaton.
Is it possible to control this operation with secret password?

The secret key should be protected by a passphrase. In this case, exporting the secret key does not help the attacker.

Note that in public key cryptography, a passphrase is not required for encryption or verification. (only for decryption and signing).

Also note that if somebody can take your computer, you have many other problems to worry about as well. For example, he could install a key logger to spy on you etc.