We propose TaintLock, a lightweight dynamic scan data authentication and encryption scheme that performs perpattern authentication and encryption using taint and signature bits embedded within the test pattern. To prevent IP theft, we pair TaintLock with truly random logic locking (TRLL) to ensure resilience against both Oracle-guided and Oracle-free attacks, including scan deobfuscation attacks. TaintLock uses a substitution-permutation (SP) network to cryptographically authenticate each test pattern using embedded taint and signature bits. It further uses cryptographically generated keys to encrypt scan data for unauthenticated users dynamically. We show that it offers a low overhead, non-intrusive secure scan solution without impacting test coverage or test time while preventing IP theft.