He just performed a bitwise XOR of the plaintext and ciphertext stream to obtain the key. From the post: By comparing the binary files, I discovered the "prop

He just performed a bitwise XOR of the plaintext and ciphertext stream to obtain the key. From the post: By comparing the binary files, I discovered the "proprietary video encryption" algorithm: for the first 15kB, each 1kB block has its initial bytes xor'd with the string "RANDOM_STRING". See: https://en.wikipedia.org/wiki/XOR_cipher https://en.wikipedia.org/wiki/XOR_cipher