Technologies for securely booting a computing device includes a security engine of the computing device that consecutively determines a hash value for each block of initial boot firmware and generates an aggregated hash value from the hash value determined for each of the blocks. A processor of the computing device determines whether the aggregated hash value matches a reference checksum value. Initialization of the processor is completed in response to a determination that the aggregated hash value matches the reference checksum value. In some embodiments, the security engine consecutively retrieves each block of the initial boot firmware from a memory of the computing device, stores each retrieved block in a secure memory of the security engine, and determines the hash value for each stored block. Each block stored in the secure memory is copied to a portion of a cache memory of the processor initialized as Cache as RAM.