Quote from: isarac3 on Today at 08:05:15 PM

I have seen an address where two transactions share similar r values and similar s values. I have once calculated a private key for a bitcoin address with two similar r values and a different s values. But this one has similar r values and similar s values.

In this case where R1=R2 and S1=S2 It's impossible to recover the private key. And it probably come from an invalid TX because in the bitcoin protocol signature you might not have two S identical

But there is different case where you can recover private key from bad use of R.

if you find for the same address two TXS with the same R and different S the private key can be easily recover with a simple formula. Before that you have to recover the Z parameter (hash of the previous tx output). If you have the private key you can easily find the nonce (k) that generate the R (supposed to be random).

After if you find an second address using the same R than above (even in only one TX). you will be able to recover the second privkey.

this case of R reusing is only possible if a issue was made on the creation of the TX
for example:
bad number random generator.
bad implementation of a TX by a developper who coded tx 'by hand'.