So libbitcoin defines the 2 functions aes256_encrypt() and aes256_decrypt().

It uses a 32 byte secret and 16 byte block size.

If I want to encrypt 5000 bytes, then I have encrypt it as 313 blocks
which is 5008 bytes right?

How can I add a password to this? Can I simply do this?

secret = bitcoin_hash("mypassphrase123")

Or should I use the scrypt function instead? How can I use that?