Quote from: johoe on January 30, 2017, 12:05:10 PM

amaclin, can you explain?

I visit this board not very often. For fast reply PM me with a link

Quote from: johoe on January 30, 2017, 12:05:10 PM

Looks like someone put a challenge for breaking weak signatures:

I think somebody is testing his bot for redeeming leaked private keys.
I was talking with some guys about cryptography and ecdsa, may be one of them
decided to join our company exploring blockchain in real-time

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https://blockchain.info/de/tx/695b04afbc477d045d396f062eeff5e950e5e44f91b7e2b273c5a74e27306177
When spending the first three outputs of this transaction, a weak signature was used.

This is not his first attempt

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The first output used k=1 when spent. This was broken immediately by a bot.

I am sure that 1ASPNUU belongs to the author of these transactions

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The second output used the same k as a previous transaction of 19iAvuzfb8uH2SZLYcbb5wtbBZdn1o3vRm.
The latter is probably a weak brainwallet or something similar. I didn't break it though. amaclin, can you explain?

You are right. But I can not tell you more info. I have a key-value database {priv₃₂->pub₃₂}
but I do not store when and where I got these datas

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The third output has k=private key. I solved the challenge and collected.

congrats!
(its a pity that my math is not so strong. i will try to solve it too.)

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The fourth output is still unsolved.
The other four outputs are not yet spent. I guess we still have to
wait for the challenge. Or maybe the address is weak for some other reason.

I doubt that this challenge would be public contest.
For my point of view somebody is testing signing bitcoin transactions with deterministic-generated
signatures for resolving the private keys of his victims later by analyzing the blockchain.
The function k () can depends on digest, public key and some other data.
for example k = digest or k = inv (digest) or even k = sha256 ( digest | pubkey )

By the way,
I have some research about 2-of-3 msig addresses with a key of 1BgGZ9tcN4rm9KBzDn7KprQz87SZ26SAMH