The software doesn't write any markers to the encrypted drive without the user's permission.
No marker available means no one is able to prove (without the password) that the drive contains encrypted data. The drive contents look like a random set of data.
The Cryptic Disk driver encrypts data in your computer's RAM immediately before writing it to the drive, and decrypts it immediately after reading. Since no extra resources are used, encryption has no effect on the read and write speed.