When will BitLocker use software-based encryption?

BitLocker utilizes software-based encryption when a Trusted Platform Module (TPM) is absent on a device. The TPM is a hardware component that enhances security by providing a secure storage for encryption keys and facilitating hardware-based encryption methods. When a TPM is not present, BitLocker must rely on the operating system's software capabilities to perform encryption tasks. This involves using software routines to handle encryption and decryption, which may not provide the same level of security and performance optimizations as hardware-based solutions.

Options involving the presence of a TPM, manual enabling, or disk formatting do not pertain to when BitLocker specifically resorts to software encryption, thus reinforcing the importance of the TPM's role in the encryption process.