February 17, 2026
Tiny crypto, huge comments
Don't pass on small block ciphers
Tiny locks, giant fight: clever shortcut or cookie-leaking disaster
TLDR: The article says small block ciphers still have niche uses for hiding counters and IDs, if used carefully. The comments explode into a brawl over using AES with format‑preserving tricks, fears about hardware instructions, and Sweet32 warnings—ending with a cautious “use them only for narrow, well-guarded jobs.”
The piece argues that “small block ciphers” — think tiny digital locks for small chunks of data — aren’t useless relics. Used carefully, they can hide counters and IDs without giving away company secrets. But the comments? Oh boy. The thread turned into a fun-size vs king-size crypto cage match.
One camp cheered, then immediately pivoted: “Just use format‑preserving encryption (FPE)”, said one top commenter, meaning keep your IDs the same size but power them with standard big-boy tools like AES that have hardware help. Another voice waved off tiny ciphers entirely: even microcontrollers — the pocket calculators of the device world — now have AES acceleration, so why reinvent anything?
Then came the tinfoil-hat twist: a commenter fretted that AES CPU instructions could secretly log your keys, prompting a chorus of “threat model: nation-state inside your chip” jokes. The spiciest clash, though, hit the article’s claim that small ciphers can be fine against “passive” snoops. A skeptic dropped the Sweet32 bomb — a well-known attack showing that 64‑bit ciphers in long-lived connections can leak cookies — and the crowd split between “context matters” and “don’t risk it.”
Pragmatists closed the loop: use tiny ciphers for short, opaque IDs only, with tricks like “cycle walking” (keep shuffling until it fits). Verdict: small blocks aren’t dead — but the community wants guardrails, not vibes.
Key Points
- •Small block ciphers (32/64-bit) are often viewed as insecure, but can be useful when applied carefully in specific protocols.
- •Larger block ciphers offer better security margins; there is a trend toward wide-block designs like Rijndael-256, Vistrutah (NIST submission), and permutations such as Keccak.
- •With 32-bit blocks, collisions become likely around 2^16 blocks per key, increasing distinguishability from random.
- •Block ciphers are keyed permutations providing forward and inverse mappings; small block sizes reduce security margins but maintain bijection properties.
- •Encrypting counters with small block ciphers can safely produce opaque identifiers without collisions within a domain and key; UUIDv4 collision behavior at scale is contrasted.