🧱 WHAT ~$25 OF AI TOKENS BUYS: A SIGNING CARD THAT NEVER SHOWS ITS KEY
Most "secure" hardware is a black box with a logo and a "trust us, it's safe". 🙄 I'm documenting the opposite: an air-gapped signer plus a smartcard applet where the spend key stays inside the chip.
Where it stands 👇 🔐 The key lives on the card, PIN-locked. In on-card mode it is never exported ✅ 329 tests green 🎯 1,380 official Monero test vectors: 0 mismatches 💣 My ring signature verifier accepts 2 signatures made by Monero itself and rejects the tampered ones 🛡 The card holds one secret and one single-use nonce. It never sees the ring or the message, and the nonce is erased BEFORE the reply leaves ⚡ A hostile host can't learn the key mod 8: the card multiplies by 8x, so small-order points die
Real bug I hit: the chip's EC unit only returns x, so the sign of the nonce commitment is invisible. No sign, no signature. Fix: two extra reference calls (4 multiplications instead of 2).
Now the honest part 👀 ❌ Nothing has run on a real card yet. Simulator only. ❌ Not audited. Keep real funds far away from it.
Next: one session on the physical card that answers a dozen open hardware questions at once. The list is public too: 33 unanswered, 10 answered.
The bill 🧾 ~$25 in AI tokens so far. Code, tests and docs all come out of that. Open source once it's validated.
If you want this to exist, tip the build and help me refund the tokens 🙏
🧱 WHAT ~$25 OF AI TOKENS BUYS: A SIGNING CARD THAT NEVER SHOWS ITS KEY
Most "secure" hardware is a black box with a logo and a "trust us, it's safe". 🙄
I'm documenting the opposite: an air-gapped signer plus a smartcard applet where the spend key stays inside the chip.
Where it stands 👇
🔐 The key lives on the card, PIN-locked. In on-card mode it is never exported
✅ 329 tests green
🎯 1,380 official Monero test vectors: 0 mismatches
💣 My ring signature verifier accepts 2 signatures made by Monero itself and rejects the tampered ones
🛡 The card holds one secret and one single-use nonce. It never sees the ring or the message, and the nonce is erased BEFORE the reply leaves
⚡ A hostile host can't learn the key mod 8: the card multiplies by 8x, so small-order points die
Real bug I hit: the chip's EC unit only returns x, so the sign of the nonce commitment is invisible.
No sign, no signature.
Fix: two extra reference calls (4 multiplications instead of 2).
Now the honest part 👀
❌ Nothing has run on a real card yet. Simulator only.
❌ Not audited. Keep real funds far away from it.
Next: one session on the physical card that answers a dozen open hardware questions at once. The list is public too: 33 unanswered, 10 answered.
The bill 🧾
~$25 in AI tokens so far. Code, tests and docs all come out of that. Open source once it's validated.
If you want this to exist, tip the build and help me refund the tokens 🙏
Tests are cheaper than trust.
Trust none. Verify everything.
Guides & tools → kavsec.agency
#SelfCustody #InfoSec #KAVSEC