These functions manage encryption and decryption of solution files. The
password must be defined in an option learnitgrid.key or an environment
variable LEARNITGRID_KEY under a digest form.
encrypt_solutions(key = NULL, error = TRUE)
decrypt_solutions(key = NULL, error = TRUE)
set_key()The key to use for encryption/decryption. If not provided, it is asked
If TRUE, an error is generate in case the file encryption or
decryption fails.
NULL invisibly.