Simplify the following text for a Grade 12 native English-speaking person.
Original: Many chosen-ciphertext attacks of practical importance are lunchtime attacks , including , for instance , when Daniel Bleichenbacher of Bell Laboratories demonstrated a practical attack against systems using the PKCS # 1 ; invented and published by RSA Security .
Simplified: A practical adaptive chosen-ciphertext attack is the Bleichenbacher attack against PKCS # 1 .