-----BEGIN BITCOIN SIGNED MESSAGE-----
Im syndria owner of this address today is October,03,2015
-----BEGIN SIGNATURE-----
17FWb5uqJRP5EkPDjwBzcMQAecHi36Jv1D
IB2RRGYJ9frwm2tKxbVpz1P+crqguOIHfsytFTmos8xuGh/rL0glgm1vYX9DsDhP8fJozT/VyVRRKC4zMRKfwck=
-----END BITCOIN SIGNED MESSAGE-----

Please Quote and verify thank you for your help

Intro:

Welcome to the world of bitcoin.

I have been a Newbie like you, looking for scrap, asking questions, working faucets. Faucets are a waste of time. Yes, it was a bit easier in the past. I could join a signature campaign with only 19 posts. Spammers have ruined this pretty much for Newbies though and if they continue I am afraid they will ruin it for all of us. This is not the topic though, sorry for the distraction. You dont believe me that I joined a campaign as Newbie? Well I can proof it to you and I can show you how. By signing a message.

The post quoted below was written by me. It was not edited and it contains a bitcoin address. If you click on its link you will see that it has no dotted line below the time and date. See here for an edited post. I changed it today. Here is a picture.


And I can sign a message with this address to prove that I still have access to the private key that belongs to this address.


You are probably not impressed. So what, a signed message, you might think, but its very important here if you want to trade with someone. There are currently at least 3 accounts in the meta section that are contested. The main problem with all of them is: someone was unable to sign a message, someone did not request a signed message for a trade or someone has no idea how to sign a message. I will try my very best to show you how to sign a message and how to verify a signed message. For this I will use pictures as I know not everyone here speaks english. I will also update this thread over time.

If you want to get your address witnessed somewhere for the future, use this thread by Tomatocage -> https://bt.irlbtc.com/view/996318.0
Someone will quote your post there to make sure a hacker that has control over your account can not change it. Make sure you only post addresses you can sign a message with. You can use this thread to test signing message, I will verify them all and Im sure other users will chime in when I am not online as well.

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Index:

• Intro
• Format
• Dos and Don'ts
• Creating a signature (ordered by date [oldest 1st])
  
  • Bitcoin Core version v0.10.0
  • Electrum v 1.9.8 (& 2.3.1)
  • MultiBit v 0.5.18
  • MultiBit HD v 0.1
  • Blockchain.info 2015.03.17
  • Mycelium 2.3.0 - 2.5.2 on Android Lollipop
  • Coinbase
  • Bither v.1.3.7.1
• Verifying a signature (in alphabetical order)
  
  • Blocktrail
  • Chain Query Alpha
  • coinig.com
  • Brainwallet.org
• Translations
• License (CC BY-SA 3.0)
  
• Services/wallets that can (currently) not be used to sign a message
  
  • ANX Vault v. 1.6 for iOS 7.1.2
  • Bitcoin Vault for iOS 7.1.2
  • Bither Hot v 1.3.9 for iOS 7.1.2
  • bitWallet for iOS 7.1.2
  • BitX Wallet 1.2.6 for iOS 7.1.2
  • Breadwallet by Aaron Voisine for iOS 7.1.2
  • Coinbase for iOS 7.1.2
  • Coinbase for Android
  • Coins v0.1 for iOS 7.1.2
  • Coins.ph v1.31 B 84 for iOS 7.1.2
  • Copay v. 1.1.3 for Windows (tested with 8.1 Pro 64 bit)
  • Copay v. 1.1.3 for Linux (tested with Ubuntu 14.04. LTS Desktop 64 Bit)
  • Copay v. 1.1.3 Chrome Plugin
  • GreenAddress/GreenBits
  • GreenAddress for iOS 7.1.2
  • Hotwallet v0.5.2 for iOS 7.1.2
  • mSIGNA
  • Wallet by Blocktrail v 1.0.9 for iOS 7.1.2
  • Xapo.com
  • Yallet for iOS 7.1.2
• Services/wallets that I did not bother to or could not test.
  
  • BitGo v1.5 - Chrome plugin, forces E-Mail verification.
  • Hive Wallet for iOS 7.1.2. - did not sync, thus I could not start the wallet in a way that would allow testing it.
  • Ninki v1.5 - Chrome plugin, forces security mechanisms in a way that makes testing for me impossible.

---

---

Format:

Note: Always include the date and reason when creating a message. If you sign a generic message it could be reused by someone else.

When you sign a message you want to present it to someone else and they want to verify the message. In order to make this extra easy its important to use a certain format. You can modify it as needed, but there are certain things to keep in mind.
Every symbol is important. The symbols > and < in my examples have to be removed. When you sign a message and somewhere have two spaces between two words, both are important for the signature. Thats the whole point of a signature. It detects whether someone changed the message or not. The board here has a "code" environment thats perfect for this. It will make sure no linebreaks are added and the other person can easily copy it. I used the same format above.

If you write a post/PM it should look like on the picture below:


and for everyone else reading, it looks like this:

I added an example how to post the signed message for the blockchain.info part here.

---

---

Dos and Don'ts:
return to index

• DO include the current date. This ensures the signature can not be reused on a different day.
• DO include the reason and be specific. This ensures the signature can not be resued for a different reason.
• DO include your nickname and where you use it. This ensures the signature can not be reused, e.g. by Shorena on AcmeCorpTalk.

---

• DO NOT use a compromised machine (virus, keylogger, etc.) to create a signature. Signing unlocks your wallets protection the same way spending bitcoin does.
• DO NOT upload your private key somewhere in order to create a signature.
• DO NOT give your private key to someone else in order to create a signature for you.

You think something is missing here? Leave a reply below.

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Creating a Signature:
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Bitcoin Core version v0.10.0
return to index

link to picture -> https://i.imgur.com/qx3C9zl.png

---

Electrum v 1.9.8
return to index
Note: Electrum 2.3.1 is exactly the same in this regard.

link to picture -> https://i.imgur.com/qXbURuy.png

---

MultiBit v 0.5.18
return to index

link to picture -> https://i.imgur.com/ftumD67.png

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MultiBit HD v 0.1
return to index

link to picture -> https://i.imgur.com/MtDpQjq.png

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Blockchain.info 2015.03.17
return to index

Note: Blockchain.info is an online wallet, thus their interface could change. Since there is no version number to indicate a change I added the date. I used the stock Tor browser for this (see the URL), but its identical to the regular version. The black bar masks the wallet identifier. Its a throwaway wallet, but I tend to remove stuff like this.

link to picture -> https://i.imgur.com/cNr6wOp.png

---

Mycelium 2.3.0 - 2.5.2 on Android Lollipop
return to index

Note: In order to get a preformatted message select "Share Text + Signature" at the last step, open with e.g. your Mail programm and copy the complete message from there.

link to picture -> https://i.imgur.com/lNgSoEq.png

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Coinbase
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See their how to for now: https://support.coinbase.com/customer/portal/articles/1526413-how-do-i-sign-a-message-with-a-bitcoin-address-

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Bither v.1.3.7.1
return to index

link to picture -> https://i.imgur.com/7Ceew9W.png

---

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Verifying a Signature:
return to index

Blocktrail
return to index

link: https://www.blocktrail.com/BTC?verifysignedmessage=1

Note: This service requires JavaScript and might not work with all browsers.

Correct Signature

link to picture -> https://i.imgur.com/CSI1CeX.png



Incorrect Address

link to picture -> https://i.imgur.com/4aWAAau.png



Incorrect Signature & Modified Message

link to picture -> https://i.imgur.com/eA5Zl5e.png



Incorrect & Modified Signature

link to picture -> https://i.imgur.com/fPS8V0w.png

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Chain Query Alpha
return to index

link: http://chainquery.com/bitcoin-api/verifymessage

Correct Signature

link to picture -> https://i.imgur.com/Wxtg5gD.png



Incorrect Signature & Modifed Address

link to picture -> https://i.imgur.com/AnDpyYW.png



Incorrect Signature & Modified Message

link to picture -> https://i.imgur.com/kOLx0K8.png



Incorrect & Modified Signature

link to picture -> https://i.imgur.com/Nvs7wtY.png

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coinig.com
return to index

Will be added ASAP Seem to be bugged when verifying messages with at least one linebreak. Will add them once its fixed.

---

Brainwallet.github.io
return to index

Note: 2015.08.08: Brainwallet is no longer operational, old pictures still linked below.

Note: 2015.04.03: I noticed the site was improved since I made the picture below. The updated version now allows to input the address, the message and the signature seperately as bitcoin-qt/core would. Since the old way is still working, I did not update the picture.

link: https://brainwallet.github.io/#verify

Correct Signature

link to picture -> https://i.imgur.com/75MFIiH.png

Incorrect Signature & Missing Address

link to picture -> https://i.imgur.com/GD2tzVJ.png

Incorrect Signature

link to picture -> https://i.imgur.com/okc8Q2K.png

---

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License (CC BY-SA 3.0):
return to index

You are free to:

• Share - copy and redistribute the material in any medium or format
• Adapt - remix, transform, and build upon the material

for any purpose, even commercially. I cannot revoke these freedoms as long as you follow the license terms.

Under the following terms:

• Attribution - You must give appropriate credit (mentioning my name [shorena] is enough), provide a link to the license, and indicate if changes were made.
• ShareAlike - If you remix, transform, or build upon the material, you must distribute your contributions under the same license (see link).

link -> https://creativecommons.org/licenses/by-sa/3.0/

Signed version:

---

todo:


changelog:

-snip-
No but I mean if my message is 1 letter, and I sign that is pretty vulnerable no?

For example:

Message:

Signature:

Address:

Private Key:

Is there any way to reverse engineer the private key if I sign the message A with the private key, and reverse engineer the private key from the message with the public key?

Here is this example i signed the message "A" with that private key and you get that signature. So i`m just curious if its possible to reverse engineer it because the message is very short?

Nice topic shorena, don't know how i didn't notice it.
I think that if someone could stick all useful links of the important posts in btctalk like this one in 1 sticky topic (like newbie readme which contains only the basics info) , it will be way helpful for all the forums members.

Maybe I missed this or just don't understand, but what's the point in adding this signature?

No, only admins can do that. They usually require a signed message though. If the guides above are not helping, let me know which wallet software/service you use. I can check whether they allow signing and make a guide is possible.