How to sign a message?!

The author of this thread is inactive for a very long time( more than a year) and the images are broken, I decided to fix the broken images. As LTU_btc suggested, when Financisto was requesting from author to add this to his tutorial.

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.

Quote from: shorena on December 07, 2013, 04:59:16 PM

19 posts... im in

18uTXyQubfaYrkbQDdaXhzd2ALEY5YN77B

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.

Code:

-----BEGIN BITCOIN SIGNED MESSAGE-----
This is shorena from bitcointalk.org and today is 2015.03.14
or as some of you might write it 03/14/15 pi day 2015
-----BEGIN SIGNATURE-----
18uTXyQubfaYrkbQDdaXhzd2ALEY5YN77B
IFtLgDZCpvfw0DT70RCLcYXj3Dbjf68sc6pj/C+u5K6IC8PIhHE4Y/ldllt1/yhrZpVW/shFRf7rxQYdsW/CcBM=
-----END BITCOIN SIGNED MESSAGE-----

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://bitcointalk.org/index.php?topic=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.

If you want to thank me because this thread has helped you, post a signed message. If you just tell me it helped you, Ill probably think you never even bothered to read this.

Index:

Intro
Format
Dos and Don'ts
"multi-sig" or pay to script hash addresses (those with the 3)
Creating a signature (ordered by date [oldest 1st])
Verifying a signature (in alphabetical order)
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
- BitGo.com (2016.07.31)
- Bither Hot v 1.3.9 for iOS 7.1.2
- Bither Hot v 1.6.1 for Android 6.0.1 with HD Wallet
- bitWallet for iOS 7.1.2
- BitX Wallet 1.2.6 for iOS 7.1.2
- Blockchain.info v6.1.38 for Android 6
- Breadwallet by Aaron Voisine for iOS 7.1.2
- Breadwallet v34 for Android 6
- BTC wallet by freewallet.org v1.0.38 for Android 6
- Coinbase for iOS 7.1.2
- Coinbase for Android
- Coinomi v1.6.5 for Android 6
- Coins v0.1 for iOS 7.1.2
- Coins.ph v1.31 B 84 for iOS 7.1.2
- Coins.ph v2.6.08 for Andoird 6
- 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
- Electrum 2.7.12 for Android 6
- GreenAddress/GreenBits
- GreenAddress 0.0.82 for Android 6
- GreenAddress for iOS 7.1.2
- Hotwallet v0.5.2 for iOS 7.1.2
- mSIGNA
- Samourai v0.89 for Android 6
- Wallet by Blocktrail v 1.0.9 for iOS 7.1.2
- Wallet by BTC.com v 2.2.7 for Android 6.0.1
- 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:

Code:

-----BEGIN BITCOIN SIGNED MESSAGE-----
<insert message here>
-----BEGIN SIGNATURE-----
<insert address here>
<insert signature here>
-----END BITCOIN SIGNED MESSAGE-----

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

Dos and Don'ts:
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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.

Pay to script hash (P2SH) addresses:
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There is no way for pay to script hash addresses without private key (yes, they are possible) to sign a message. For multi-sig-addresses (a subset of P2SH addresses) there are private keys, but there is no consistent definition on how a signature for a message would be verified. Thus, its impossible to sign a message with an address starting with a 3 in a realiable way. With the addition of P2SH-P2WPKH addresses (SegWit, but starting with a 3) this did not change. At least it did not in bitcoin core, other wallets may still allow signing or verification.

Creating a Signature:
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Bitcoin Core version v0.10.0
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Electrum v 1.9.8
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Note: Electrum 2.3.1 and 2.5.4 are exactly the same in this regard.

MultiBit v 0.5.18
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MultiBit HD v 0.1
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Blockchain.info
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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.

Blockchain.info v2 2016.05.11
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Update (2017.5.13): According to user apoorvlathey it is now possible to sign messages with the new version as it was in the past. User sHeRiLyN1618 reports that this is only possible for imported addresses, but not addresses generated with the service. For more information read the posts starting from here -> https://bitcointalk.org/index.php?topic=990345.msg18991565#msg18991565

Update (2016.5.11): It is now possible to sign messages with imported private keys.
Th0ur007 wrote a step by step here -> https://bitcointalk.org/index.php?topic=1467458

Note: Blockchain.info's new wallet does not allow you to sign a message, nor does it allow you to easily export the private key in order to sign with a different wallet. There is a crude work around here -> https://docs.google.com/document/d/1-2l6xOqcbjs9QWEqSh72RD1d8EEdvG_hQuEXw_f_o6w/edit
Use at your own risk!

Mycelium 2.3.0 - 2.5.2 on Android Lollipop
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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.

Coinbase
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Note: 2018.03.04 coinbase has removed the tutorial.

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

Bither v.1.3.7.1
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Ledger Wallet Bitcoin v.1.10.1
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Note! full credit for this section goes to JeremyB. Go thank them, not me!

Trezor Wallet
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Note: full credit for this section goes to JeremyB. Go thank them, not me!

Verifying a Signature:
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Blocktrail
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link: https://www.blocktrail.com/BTC?verifysignedmessage=1

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

Correct Signature

Incorrect Address

Incorrect Signature & Modified Message

Incorrect & Modified Signature

Chain Query Alpha
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link: http://chainquery.com/bitcoin-api/verifymessage

Correct Signature

Incorrect Signature & Modifed Address

Incorrect Signature & Modified Message

Incorrect & Modified Signature

coinig.com
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~~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
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Note: 2018.03.02: New link https://brainwalletx.github.io/#verify

Note: 2015.12.20: Brainwallet has a copy here -> http://wallet-2sx53n.sakurity.com/#verify

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 pictures.~~ Thanks 2 [/url=https://bitcointalk.org/index.php?topic=990345.msg31257348#msg31257348]JeremyB[/url] for updating the pictures.

link: ~~https://brainwallet.github.io/#verify~~ copy: http://wallet-2sx53n.sakurity.com/#verify

(Bitcoin-QT) Correct Signature

(Bitcoin-QT) Incorrect Signature

(Bitcoin-QT) Correct Signature & Missing address

Correct Signature

Incorrect Signature & Missing Address

Incorrect Signature

Trezor
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Note: full credit for this section goes to JeremyB. Go thank them, not me!

Correct Signature

Incorrect Signature

License (CC BY-SA 3.0):
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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:

Code:

-----BEGIN BITCOIN SIGNED MESSAGE-----
This is shorena from bitcointalk.org and today is the 24th of April 2015.
I publish my guide to sign message with bitcoin addresses and all related pictures under CC BY-SA 3.0
link to guide  : https://bitcointalk.org/index.php?topic=990345.0
link to license: https://creativecommons.org/licenses/by-sa/3.0/
-----BEGIN SIGNATURE-----
18uTXyQubfaYrkbQDdaXhzd2ALEY5YN77B
IDYQyGOx2rG9aJ3bZH/SJSRFZJMZiMrIxiNNY1Hv9geHLlYeGdYbH+AxNbT+qXGmEzojFt//loC+sj8yGo6AV9A=
-----END BITCOIN SIGNED MESSAGE-----

todo:

Code:

https://tools.bitcoin.com/verifier.html - verify
https://blockexplorer.com/messages/verify - verify
Bither v 1.3.7.1 - verify
Bitcoin Core version v0.12.0 - verify
Electrum 2.x - verify
Blockchain.info - verify
Multibit - verify
Multibit HD - verify
list more wallets/services that currently not support signing, add reference where possible
coinbase (own w/o text)
armory
(when fixed) coinig.com - verify

changelog:

Code:

2018.03.04 - added Filipino translation done by uelque, coinbase how to no longer available.
2018.03.02 - added Trezor sign/verify, ledger sign, brainwalletx updated pictures & french translation all done by JeremyB
2017.05.13 - bc.iv2 - working
2017.03.24 - Bither Android HD -> cant sign
2016.12.14 - "thanks" w/o signed message = idiot/spammer/or worse
2016.12.11 - added btc.com, freewallet.org, GreenAddress, breadwallet, Coinomi, Electrum, Coins.ph. Samourai and blockchain.info for android as cant sign.
2016.07.31 - added bitgo.com as cant sign.
2016.05.11 - Updated bc.i v2 with link to Th0ur007's guide.
2016.04.17 - added a few sentences on p2sh addresses
2016.03.04 - added work around for bc.i v2
2015.12.20 - readded brainwallet via a mirror, reinstated the pictures
2015.10.01 - problem with blocktrail was fixed, removed the warning and reinstated the pictures
2015.10.01 - added warning because blocktrail has problems verifying certain messages
2015.09.17 - added notes how each section is sorted
2015.09.17 - changed all imgur links/sources to https
2015.09.17 - added Bither v 1.3.7.1 (screenshots Ubuntu, Windows identical)
2015.09.17 - added several Copay (several version) to cant sign
2015.09.17 - added didnt bother to test section
2015.09.16 - added blocktrail.com - verify
2015.09.11 - sorted cant sign by name
2015.09.11 - added several more iOS 7.1.2 wallet to cant sign: Coins, ANX Vault, GreenAddress, BitX, Bitcoin Vault, Coins.ph
2015.09.11 - added Coinbase for Android thanks to prodigy8
2015.09.11 - updated todo list (blocktrail verify)
2015.09.10 - added several iOS 7.1.2 wallets to cant sign: bitWallet, breadwallet, Coinbase, Yallet, Wallet by Blocktrail, Bither Hot and Hotwallet
2015.08.12 - updated todo
2015.08.12 - added chain query alpha - verify - pictures
2015.08.11 - added link to chain query alpha - verify
2015.08.10 - added greenbits/-address to cant sign
2015.08.09 - temp removed coinig.com as it seems to be broken when verifying messages with linebreaks
2015.08.08 - temp added coinig.com to replace brainwallet - no pictures
2015.08.08 - brainwallet - verify no longer operational
2015.08.07 - added mSIGN and xapo to cant sign
2015.08.07 - added "cant sign" section
2015.07.27 - added first translation to romanian - thanks to Saruman
2015.07.27 - added list of translations
2015.07.20 - improved formatting - thanks to Muhammed Zakir
2015.07.09 - added link to coinbase how to - thanks to camelson
2015.06.22 - added multibit hd 0.1 - sig
2015.06.15 - did not add electrum 2.3.1 because its idential to 1.9.8, added text accordingly
2015.04.25 - added don't "compromised sys" - thanks to Muhammed Zakir
2015.04.24 - slightly changed license text (cosmetical changes)
2015.04.24 - added dos and don'ts - thanks to GreenStox
2015.04.19 - added link address stake thread - thanks to Muhammed Zakir
2015.04.12 - added license CC BY-SA 3.0
2015.04.03 - format, added note: use a date
2015.04.03 - brainwallet verify, added note: new "Bitcoin-QT"-Button
2015.04.03 - added Mycelium 2.3.0 on Android Lollipop
2015.03.17 - updated todo
2015.03.17 - added bc.i - sig
2015.03.15 - MultiBit 0.5.18 - sig
2015.03.15 - Electrum 1.9.8 - sig
2015.03.14 - Brainwallet online verify (Tor) - verify
2015.03.14 - Bitcoin Core version v0.10.0 - sig
2015.03.14 - Index
2015.03.14 - added Intro
2018.09.29 - Link to russian version by an@sha