"Sign Message" and "Verify Message" working

[jim618]

I have got "Sign Message" and "Verify Message" working.
This is pretty similar functionality to the Satoshi client.

Screenshots:






I have only just got them working so there is all the field validation, finishing off to do yet.
I expect they will appear in the next version, 0.5.11

[freemoney458]

Hi Jim,

that is a very nice feature, Jim.

Please forgive me my noob questions:

How is the signature created?
Is it possible to derive from the signature the private keys?
Does a signed message cost something?
Who receives the signed message?
Is it send to the whole bitcoin network?
Or do I have to copy it to e.g. an email?

Could you come up with some use cases?

Is it possible to verify that a payment address is untampered by an attacker?
How would this work?

Is it possible to set up contracts?
How would this work?

Is it possible to proove that I control a specified address?
How would this work?

Is it possible to create multisignature addresses with this feature?

[jim618]

Hi Freemoney,

It is quite similar to other signing algorithms, in that you take the message, hash it and then use the same 'Bitcoin signing' (ECDSA) that is does for transactions to create a signature. This uses the private key of the address you choose. From the signature you can work out the address used to sign it but not the private key.

It costs nothing and nothing is sent to the network. Everything is performed locally.

One of the uses of signatures at the moment is with the addresses used for mining dues. Say I have some mining dues going to an address 1abc and I want to change it to an address 1def. The mining pool want to know I own the private key for address 1abc. If I write a message:

I own the address 1abc and from now on want all the mining dues to go to address 1def

And then sign it with address 1abc the mining pool knows it is legitimate.

You can use it like PGP signing if you have a well known address. For instance I have a donations address on multibit.org. I can sign messages (say multibit release messages) with it and other users can check it.

One of the things I am going to program up is that the 'there is a new version of multibit' file will be signed. That way MultiBit can check it is legitimate when it accesses it.

Initially it will be signed by the multibit.org donation address but it will be subsequently threshold signed '2 of 3' by myself, Tim Molter and Gary Rowe. It will need 2 or more valid signatures from specific addresses controlled by Gary, Tim and I before the message is believed.

It is a general purpose signing technique so you can use it anywhere you want a cryptographic signature of a message.

[mjb]

This is great - the last missing feature that forced me to open the satoshi client from time to time!

Donation underway...

[jim618]

Thanks !

[lunarboy]

Hi Jim

Any idea why I can't copy or paste into any of the sign or verify address/message/signature fields? its been causing me headaches for a while now.

Is there a way to turn on this ability as it seems deliberately restricted?

Thanks

Lunar

[filchef]

Hi Jim

Any idea why I can't copy or paste into any of the sign or verify address/message/signature fields? its been causing me headaches for a while now.

Is there a way to turn on this ability as it seems deliberately restricted?

Thanks

Lunar

With key combination Ctrl+v you can paste address with Ctrl+c you can copy signature and message - first you have to mark them with mouse.

[lunarboy]

Hi Jim

Any idea why I can't copy or paste into any of the sign or verify address/message/signature fields? its been causing me headaches for a while now.

Is there a way to turn on this ability as it seems deliberately restricted?

Thanks

Lunar

With key combination Ctrl+v you can paste address with Ctrl+c you can copy signature and message - first you have to mark them with mouse.

have you tried turning it on and off again?  

no seriously... running the 0.5.15 version on OSX  copy and paste in these fields is not currently possibly. Maybe its a bug?

edit: fixed now, think it was an issue with the mavericks update.