Nonce Reuse Attack
- If you prefer reading on the website, check π https://bitcoindevs.xyz/decoding/nonce-reuse-attack
Nonce is a random, unique value used in the signing process.
In Schnorr signatures, each signature requires a fresh nonce. Reusing the same nonce is a dangerous mistake that allows an attacker to calculate your private key.
Let's start by breaking down the Schnorr signature equation to see how this happens.
If the nonce k remains the same across different transactions, an attacker can isolate the private key d by comparing two signatures.
Imagine you want to sign two separate transactions but mistakenly use the same nonce for both. Here's how it plays out:
Hereβs where things go wrong when the nonce is reused!
Since the only variable difference between S1 and S2 is the hash of the transactions, an attacker can calculate k and subsequently derive your private key d. This exposes your Bitcoin funds to theft.
How to Prevent Nonce Reuse Attacks ?
The solution is straightforward:
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Never reuse a nonce!
Always ensure that your cryptographic library generates a unique, random nonce for each signature.
6. Calculating the Private Key from Reused Nonces
Check π https://bitcoindevs.xyz/decoding/nonce-reuse-attack for the explanation