Guides

The background behind the tools

Longer reads on how the underlying formats, ciphers, and conventions actually work - with worked examples that were computed and verified, not copied.

Security
Fixing Jasypt ENC() decryption failures in Spring Boot
Why EncryptionOperationNotPossibleException happens: the PBEWithMD5AndDES byte format, the jasypt-spring-boot 3.0.0 default change, and ranked fixes.
Encryption
AES ECB vs CBC, shown at the byte level
Encrypt the same plaintext block three times in ECB and CBC and read the hex: why ECB leaks structure, why IV reuse hurts CBC, and where GCM fits.
Security
Why bcrypt and not MD5: the cracking-cost math
Real GPU benchmark numbers: MD5 falls to an 8-char brute force in 1.3 seconds, bcrypt cost 12 takes 4.6 years. The arithmetic, verified.
Developer
Reading a JWT by hand: exp, iat, nbf and the traps
Build and verify an HS256 JWT from raw bytes: base64url vs base64, unix-time claims, clock skew, and the alg=none attack.
Developer
The 20 cron expressions everyone copies, explained
The 20 most-copied cron expressions and the next-run times they produce, plus the DOW 0-vs-7, OR-semantics, */N alignment, and DST traps behind each one.
Developer
JavaScript regex vs PCRE: the differences that bite
A feature-by-feature comparison of JavaScript RegExp and PCRE2: lookbehind, atomic groups, \A/\z, inline modifiers, the v flag, and silent Annex B traps.
Documents
Editing Excel without Office: what a browser formula engine really supports
Exactly which Excel functions work in a browser spreadsheet editor, which return #NAME?, and what survives xlsx and csv export.
Documents
What survives a .docx round-trip in a browser editor
A tested inventory of which Word features survive docx-to-browser-to-docx editing: what mammoth keeps, what the export drops, and why.
Developer
Base64: why your files grow 33% and when that is fine
The exact math behind Base64's 33% size overhead, padding, base64url, data URIs, MIME, and when you should not Base64-encode files at all.
Product
Sharing text and files between devices without an account: how ClipVault boards work
How ClipVault's live boards sync text and files across devices with no account — Firestore real-time sync, PIN locks, file expiry, and where the design stops.