Encryption-key.bin File -

openssl enc -d -aes-256-cbc -in secret.enc -out secret.txt -K $(xxd -p -c 32 encryption-key.bin) -iv 0

Decryption reverses the process:

At its core, a .bin file is a generic binary container. When labeled as an encryption-key.bin, it serves as the "physical" lock or digital signature for an encrypted volume or database. In symmetric encryption, this file might hold the single key used for both locking and unlocking data. In asymmetric setups, it may contain a private key used to decrypt information that was encrypted with a corresponding public key. Common Uses for Encryption-Key.bin encryption-key.bin file