Hey everyone,

I came across a weird case while digging into some old addresses that reused the same nonce k (same R value in the signature), but across different private keys. Original thread here: https://bitcointalk.org/index.php?topic=5535021.0

The setup:
Three addresses (let’s call them A, B, and C) all sent funds to the same destination at the exact same second.

I have the private keys for A and C — not B.

Here’s what’s interesting:
The private keys of A and C have a GCD of 63, meaning they are both exactly divisible by 63 — i.e.,
I found other key pairs with GCDs of 18, 27, etc.dA = a × 63
dC = b × 63

I’ve also found other key pairs with GCDs of 18, 27, etc. This suggests some kind of structure or weakness in how these keys were generated.

My question:
Could this GCD link help reduce entropy or even lead to the missing key (B)?

Thanks in advance!

Hey everyone,

I came across a weird case while digging into some old addresses that reused the same nonce k (same R value in the signature), but across different private keys. Original thread here: https://bitcointalk.org/index.php?topic=5535021.0

The setup:
Three addresses (let’s call them A, B, and C) all sent funds to the same destination at the exact same second.

I have the private keys for A and C — not B.

Here’s what’s interesting:
The private keys of A and C have a GCD of 63.
I found other key pairs with GCDs of 18, 27, etc.

My question:
Could this GCD link help reduce entropy or even lead to the missing key (B)?

Thanks in advance!