keystore: pass private key to nonce_commit() and sign() #1534
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End-goal: reduce the number of secure chip ops when signing a BTC transaction, to reduce the chance of going over the Optiga chip's "rate limit", which induces throttling. With antiklepto, we derived the private key twice for each input that is signed: once to commit to the nonce, and after that to sign. This commit decouples the nonce commit and sign functions from the underlying keystore, and allows reusing a private key instead of re-deriving it, which requires secure chip operations. This halves the number of secure chip ops needed per input when signing a BTC transaction. We do not reuse the privkey for the other instances of antiklepto (signing a msg, signing an ETH tx), as there it's one commit/sign pair only and unlikely to cause secure chip throttling.
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End-goal: reduce the number of secure chip ops when signing a BTC transaction, to reduce the chance of going over the Optiga chip's "rate limit", which induces throttling.
With antiklepto, we derived the private key twice for each input that is signed: once to commit to the nonce, and after that to sign.
This commit decouples the nonce commit and sign functions from the underlying keystore, and allows reusing a private key instead of re-deriving it, which requires secure chip operations.
This halves the number of secure chip ops needed per input when signing a BTC transaction.
We do not reuse the privkey for the other instances of antiklepto (signing a msg, signing an ETH tx), as there it's one commit/sign pair only and unlikely to cause secure chip throttling.