Practical security notes: password recovery, TLS certificates, SSH keys and network security — tools and procedures explained step by step.
fcrackzip is a small, old, command-line tool that recovers passwords on classic-ZipCrypto-encrypted .zip files. Brute-force or dictionary, runs everywhere, still useful in 2026 — with hashcat/john as the modern follow-up when it isn't fast enough.
pdfcrack is a small, single-threaded CPU tool for recovering lost PDF user and owner passwords. Fine for 40-bit RC4 and small dictionary attacks; for 128/256-bit AES PDFs, migrate to pdf2john + hashcat on a GPU.
Passwordless sudo is convenient for automation and lab boxes — and a foot-gun if you do it carelessly. Here's the modern, safe way: a validated drop-in under /etc/sudoers.d, scoped as narrowly as you can get away with.
OpenSSL can decode a CSR so you can confirm the subject, SANs, and key size before sending it to a CA. Here's the one command to read it, plus how to verify a CSR matches the private key it was generated from.
OpenSSL reads X.509 certificates so you can check the subject, SANs, issuer, and expiry — and confirm a cert matches the private key it's paired with. Includes the s_client trick for inspecting what a live HTTPS server is really serving.
rarcrack is long abandoned. The 2026 way to recover a RAR/7z/ZIP password is to extract a hash with John the Ripper's rar2john/7z2john/zip2john, then run it through hashcat (GPU) or john. Dictionary first, then masks. Covers the right hashcat mode for each format.
There are two very different 'Word passwords'. Editing/read-only protection is trivial — a .docx is a ZIP, so you delete one XML element and it's gone. Password-to-open is real AES encryption and has to be cracked with office2john + hashcat. This post covers both, honestly.
Password-free SSH is key-pair authentication: a private key stays on your machine, the matching public key goes on the server. Generate an ed25519 key, copy it with ssh-copy-id, lock down the permissions — and, if you want, turn password logins off entirely.
An encrypted private key makes Apache/nginx prompt for a passphrase on every start — a problem for unattended reboots. OpenSSL can write an unencrypted copy. Here's how, for RSA/EC/any key, plus why you should lock the file down and what the safer alternatives are.
Java's default truststore (cacerts) password is 'changeit' — and has been forever. Here's where the file lives in a modern JDK, plus the keytool commands to list trusted CAs, import a self-signed/internal certificate, and actually change that password.