The beginner course taught you what encryption, hashing, and signatures are. Here you use them. Every topic runs a real command in the Meridian lab — encrypting a backup, hashing a password the right way, reading a TLS handshake — and the chapter ends with you able to protect Meridian's data in transit and at rest, and to spot the crypto mistakes that quietly void all of it.
7 topics
Cryptography fails in practice far more often through misuse than through broken math. The algorithms — AES, SHA-256, RSA, elliptic curves — are sound; what breaks is the mode chosen, the nonce reused, the key committed to git, the fast hash used on a password. This chapter is about using the sound primitives correctly, on Meridian's real data.
Seven topics move from symmetric encryption to the usage mistakes that undo it. Along the way you protect a database backup, store passwords so a stolen table is nearly useless, exchange keys over a channel an eavesdropper is watching, and open the black box that the beginner course drew as a padlock. The rule underneath all of it: use vetted libraries and standard constructions, and never roll your own.
Four jobs, four tools — do not use one where you need another