Ask a related question, about 3DES encryption, know clear text and ciphertext, can launch the key?

Ask a question, about 3DES encryption, know clear text and ciphertext, can launch key?
Hello, because the previous days to develop a dongle, built-in 3DES algorithm, the use of 24 letters to do the key, encrypt 24 digits, if you know clear text and ciphertext, can launch the key it, thank you
------to solve the idea----------------------
The simple point is whether the ciphertext will change every time if the encryption will have a new ciphertext appear ...
------to solve the idea----------------------
If the cipher is different every time, it will be difficult to launch.

