Author

Topic: Can signmessage be used to spend coins? (Read 688 times)

legendary
Activity: 1135
Merit: 1166
June 22, 2013, 12:46:30 AM
#3
All messages signed with the signmessage command have "Bitcoin Signed Message:\n" prepended to them for exactly this reason.

That is what I supposed, thanks for confirming it! Smiley
legendary
Activity: 1526
Merit: 1134
June 21, 2013, 03:39:24 PM
#2
All messages signed with the signmessage command have "Bitcoin Signed Message:\n" prepended to them for exactly this reason.
legendary
Activity: 1135
Merit: 1166
June 21, 2013, 02:25:10 PM
#1
I'm working on a project which will require users to sign server-provided challenge messages with the private key of one of their addresses.  Since a signature with that key is basically also what allows to spend coins from that address, I want to be sure about the security implications for my users.

Assuming a user can be tricked to "signmessage" arbitrary strings provided by an attacker, can this be used to spend the user's coins?  I presume there is some safeguard in the protocol such that the data signed with signmessage is of a different "format" than signing of transaction outputs ... is this the case, or can a message be crafted such that the signature on it can be recast in a form to validate spending a transaction output?

Of course my server is not going to issue rogue challenges to sign, but before I tell people to sign randomly provided strings and make them used to it, I want to make sure this can't be used to attack their coins.
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