openssl rand -base64 32 > key.bin
2. Encrypt key openssl rsautl -encrypt -inkey id_rsa.pub.pem -pubin -in key.bin -out key.bin.enc
3. Encrypt file using key openssl enc -aes-256-cbc -salt -in SECRET_FILE -out SECRET_FILE.enc -pass file:./key.bin
-- other side -- openssl rsautl -decrypt -inkey id_rsa.pem -in key.bin.enc -out key.bin
5. Decrypt file openssl enc -d -aes-256-cbc -in SECRET_FILE.enc -out SECRET_FILE -pass file:./key.bin
Ideally you'd want to coat any metal surface with black epoxy, and set the IR camera Emissivity Coefficient to 0.9 (the coefficient for black epoxy).