How to initialize Blockstream Green Wallet?

How to export a private key

Exporting a private key makes it possible to transfer a Bitcoin address to another software. It can also be used to back up Bitcoin addresses that can be re-imported as needed. Attention, the private keys can allow to use the funds associated with these addresses. It is therefore advisable to protect them by encryption or to keep them on paper only.

With BitcoinCore

It is not recommended to use a private key simultaneously with the Bitcoin Core software and an online wallet, otherwise the Bitcoin software may malfunction. To fix this error, it would then be necessary to export the private keys, reinstall Bitcoin QT and re-import the private keys.

Export steps:
– Open your Bitcoin Qt software
– Click on the Help / Debug window menu (at the top).
– Click on the Console tab .
– If your wallet is encrypted, type the following command followed by the Enter key to unlock your wallet: walletpassphrase (your password) 600
– Type the following command to export the key: dumpprivkey (Bitcoin address) – The private key is displayed on the screen and you just have to highlight it and copy it. 

How to import a private key

Importing a private key allows you to switch Bitcoin wallet software or services without having to switch Bitcoin addresses. It can also be used to restore addresses saved for security.

Attention :

1. Private keys can allow funds associated with these addresses to be used. It is therefore advisable to protect them by encryption or to keep them on paper only.

2. When performing an import operation for the first time, do so first with very small amounts. Don’t risk your savings until you’re confident.

3. Use a healthy computer protected by anti-virus. If you have any doubts about the hardware you are using, a hardware  wallet  might come in handy.

With Electrum

After installing the application (Android, Linux or Windows), create a new wallet (if you already have a wallet on Electrum, go to the three dots at the top right of the android app). Click on “New”, give the wallet a name and then choose “Import Bitcoin address or private key”. You can then copy/paste the private key or scan the private key. Warning: these operations are delicate and insecure. As soon as the key is imported, it is recommended to send the funds without delay to an address generated in the rules of the art (for example with a hardware wallet) or to a trusted exchange platform.

With Blockstream Green:

Obsolete (valid only for old versions): After installing the application (Android or Ios) and saving the recovery words that the application will generate for you when creating a new wallet:
– Go to  “receive”
– Go to  “More Options”
– Click on  “Swipe from Paper Wallet”
– Scan the QR code of the private key or enter the 51 characters of the private key by hand (this key starts with a 5)
– On the application  Blockstream Green  click  “Next”
– The application will perform a transaction on a new address. Depending on the level of fees you have chosen, it will take more or less time (from a few minutes to a few hours)
– When the transaction is confirmed, you can now spend your bitcoins from the application.

With  Greenaddress  :

Follow the following path: “  Receive > Show advanced options > Private key in WIF or BIP38 format ”. Then enter the 51 characters of your private key.

With Copay  :

Click on “  Scan”  then scan the QR code of your private key. If you do not have this QR code you can generate it from  by following the following path: “  Wallet Details/Détails du Porte-Monnaie > Enter Private Enter the Private Key > View details/See details “.

With BitcoinCore  :

It is not recommended to use a private key simultaneously with the Bitcoin Core software and an online wallet, otherwise the Bitcoin software may malfunction. To fix this error, it would then be necessary to export the private keys, reinstall Bitcoin QT and re-import the private keys.

Import steps: 
– Open your Bitcoin Core software
– Click on the  Help / Debug window menu  (at the top).
– Click on the  Console tab .
– If your wallet is encrypted, type the following command followed by the  Enter key  to unlock your wallet:  walletpassphrase  (your password)  600
– Type the following command to import the key: importprivkey (private key) (label ) 
– Wait patiently for the import to complete. The software will not respond for several minutes. We must wait and we must not close the software while it has not completed the import. The import is complete when the console is ready to receive a new command. Close and open the Bitcoin software to refresh it.

Set up a Green Wallet


How to Create a Custom Bitcoin Address

Here is a little tutorial that will allow you to personalize your Bitcoin addresses on a few characters.

Warning: This program is useful only to those who are able to verify the origin of the code and its integrity. In all other cases, a “hardware wallet” is a better solution for generating keys (which however will not be customizable).

When entering the world of cryptocurrencies, you will quickly hear about Bitcoin addresses. They are an integral part of securely storing Bitcoin (BTC) and also sending and receiving it. Here you can find out how to get a Bitcoin address and what you should know about it.

Bitcoin (BTC)  as the mother of all cryptocurrencies has long since attracted widespread interest and not only in the Corona times do many citizens think: Bitcoin seems to be a suitable instrument to protect their assets from the risk of inflation and at the same time to be able to hope for increases in value. If you then want to turn theoretical considerations into reality, the topic of Bitcoin addresses will be one of the first that you should solve. So what is a BTC address and how do you get one or more of them:

  1. In principle, a Bitcoin address is what is referred to as an account number in the classic banking world. Credit is stored under it, BTC can be sent from it and BTC can also be received at a Bitcoin address.
  2. There are three widely used formats for Bitcoin addresses, we have listed the details. All three formats have one thing in common: A Bitcoin address is generated mathematically from the interaction of public and private key. The public key serves as a clear assignment to an account holder, the private key allows access to credit and the sending of BTC.
  3. There are again three options to have your own Bitcoin address generated: use a mobile wallet, hardware wallet or the service of crypto exchanges. Other options that are advertised are generally to be classified as dubious and you should absolutely avoid them.

Bitcoin Address Through Mobile Wallet : Transaction and trade BTC anywhere on the go? Then you need a mobile wallet and this will also help you to get a Bitcoin address. The first port of call for downloading a mobile wallet to your smartphone is the Apple App Store for iPhones or the Google Play Store for Android devices. Proven mobile wallets include Electrum, Jaxx Liberty and BRD. When setting up the mobile wallet, you will create a Bitcoin wallet. This is usually protected by an additional pin code and/or a recovery phrase. With the latter you can restore your wallet if your device is lost, defective or stolen.

A Bitcoin address is also generated in the mobile wallet. The private key stays with you, it is your final key to this account. The public key allows Bitcoin to calculate addresses that can be clearly assigned to you. When choosing a mobile wallet, you should definitely access the official app stores and still study the reviews. Here, too, unsafe solutions have already made it through the testing process.

Bitcoin address through hardware wallet: The safest place for your BTC is still hardware wallets. Here your bitcoin is stored shielded from the internet on a small device. We recommend the Ledger Nano S or the Ledger Nano X , because the French manufacturer Ledger has optimally combined user-friendliness and security. But the devices from the competitor Trezor have also proven themselves. In our big test of hardware wallets  you will find out everything about the pluses and minuses of the individual models.

As with a mobile wallet, a Bitcoin address is automatically generated when setting up a hardware wallet . Here, too, public and private keys should not be confused. Likewise, the recovery phrase is again your protection in the event of a defect or loss of the device.

Bitcoin address through crypto exchange: As a beginner, you will probably buy your first BTC via a crypto exchange. These providers make your first steps in dealing with Bitcoin and other cryptocurrencies as easy as possible. After registration, your customer account is either automatically linked to an integrated software wallet or you initiate this process under menu items such as “Wallet” or “Deposit”. In any case, you will also receive a Bitcoin address here – if this is not the case, then hands off. Because a missing individual Bitcoin address with public and private key means that you do not buy any real BTC from such a provider. Established crypto exchanges such as eToro , Coinbase or , above all, Binance allow you to quickly and easily buy BTC for euros and also guarantee you a Bitcoin address.

Bitcoin address in practice: Normally, your BTC wallet also offers you to display the multi-digit code of the Bitcoin address as a QR code. This makes it much easier for you, for example, to move BTC between your different wallets or to receive Bitcoin from third parties to whom you send this QR code by simply scanning the address. You do the same thing the other way around if you want to transfer BTC to a foreign Bitcoin address.

Multiple Bitcoin addresses: In principle, an infinite number of unique Bitcoin addresses can be created from your public and private key. Why is this useful? With multiple Bitcoin addresses, which you generate for exactly one transfer, your counterpart only knows this and can at most attack this one. Your main Bitcoin address remains unknown, so you use disposable addresses. This feature is supported by hardware wallets and most mobile wallets, but not all crypto exchanges.

Conclusion: Bitcoin address easier than expected

You have understood the key points about Bitcoin addresses:

  • When you set up a BTC hardware wallet , mobile wallet or customer account with a reputable crypto exchange, you will automatically be provided with a Bitcoin address.
  • You should exercise caution when selecting the service provider, unfortunately there are many providers who have no good intentions. Hardware wallet from Ledger, Binance as a crypto exchange and one of the mobile wallets mentioned – you are on the safe side.
  • Multiple bitcoin addresses for receiving BTC are another good idea for security reasons.
  • The private key(s) for your balance in Bitcoin and other cryptocurrencies, as well as the recovery phrase, remain in a safe place with you alone.
  • With this knowledge, getting started with Bitcoin should be easier than you thought.

Set up a multisig wallet

Connect your mobile wallet to your node

Connect with Electrum Personal Server

Next step in our tutorial: Electrum Personal Server.

So far we have:

  • a node to validate the blockchain ( Bitcoin Core )
  • an interface to manage our addresses and make our transactions ( Electrum )
  • a hardware wallet to protect our private keys ( Ledger )

We have a problem: Electrum is a thin client, i.e. it does not contain the blockchain and does not validate transactions. Electrum is unable to find the outputs attached to the addresses of your wallet, nor to build transactions because it requires access to the blockchain.

Electrum Servers

When you launch Electrum, you are actually connecting to a server that contains a Bitcoin node and can provide you with the information you need. By default Electrum will automatically connect to a server from a list of available servers that you can consult by clicking on the big green dot at the bottom right of the Electrum window. By unchecking the “Select a server automatically” box, you can choose the server to which you will connect.

The problem is that we installed Bitcoin Core on purpose to be autonomous on the Bitcoin network, but by using Electrum we cannot leverage our node to get the information Electrum needs on the blockchain !

One solution would be to run our own Electrum server, but this is expensive and requires a powerful machine, because we must keep all the unspent outputs in memory in order to be able to respond quickly to requests from several clients.

This is why Chris Belcher developed Electrum Personal Server, which as the name suggests is a personal Electrum server, therefore simplified and lighter that you can install with your own Bitcoin Core node to replace the Electrum servers “public”.

Retrieve the main public key of your wallet

To track our wallet created (or imported) in Electrum inside EPS, we need its main public key (master pubkey).

Today most wallets are Hierarchical Deterministic (HD). This barbaric term simply means that they always create the same Bitcoin addresses in the same order, which was not the case with previous wallets which generated addresses randomly.

To do this, an HD wallet uses a “master” or primary public key, from which all addresses are derived. To put it another way, this means that if two software or even two different machines have this public key, they will both generate the same addresses in the same order.

EPS uses this feature to track your addresses. This is why we are going to retrieve the public key in Electrum to be able to enter it in EPS later:

  1. In Electrum, click on the “Portfolio” menu, then “Information”
  2. A new window opens, with a long string of seemingly random characters
  3. Copy this character sequence and paste it somewhere where you can retrieve it easily

Download Electrum Personal Server

You can find the Windows version 1.7 file  .

Once downloaded, unzip it in a new folder, just run it by double-clicking on it like any other program.

The config file

I advise you first of all to make a copy of the file config.ini_samplewhich you will simply call config.ini.

Now open config.iniwith Notepad and make the following changes:

  • In the section [master-public-key], add a line in the following form where you will paste the master pubkey that we set aside in Electrum earlier: [wallet_name] [space] = [space] [master pubkey]In the section [bitcoin-rpc], add the path to the Bitcoin Core datadir (this is the path you gave when you first launched Bitcoin Core, see the tutorial),
  • Normally, the default configurations should suffice for the rest.

    Launch EPS

    Click on the file config.ini, keep the mouse pressed and drag until electrum-personal-server.exe, then release.

    During the first launch, EPS will first import all the addresses to follow in your node and stop, you will then have to repeat this operation to launch it.

    If it’s a wallet you haven’t made any transactions on, that’s all there is to it. Otherwise, the blockchain will have to be rescanned to find previous transactions.

    If you need a rescan, drag the configuration file to electrum-personal-server-rescan.bat.

    Connecting from Electrum

    On the Electrum side, we now need to connect to EPS.

    Click on the big green dot (or red if you are not connected to any server) at the bottom right of the window. In the new window that opens, click on the “server” tab and uncheck the box “Select a server automatically” if it is not already done.

Multisignature, an essential tool for the security of your bitcoins

What you should have

If you have followed this guide so far, you now have:

  • a Bitcoin node that validates all transactions on the network
  • Electrum Personal Server , which indexes your own transactions and tracks them through your node
  • Electrum , which provides you with a clean and easy-to-use interface
  • A Ledger , which secures your private keys against most thefts

As it stands, you already have a fairly satisfactory installation in terms of:

  • security: your private keys are not exposed to hacking. Your Ledger may be physically stolen from you, but if you have taken care to protect it with a pin and secure your seed, the thief has little chance of success.
  • confidentiality: you do not leak information about your addresses, your balances and your transactions, because you own all this information on your own node. Be careful though an attacker can still learn a lot about you and your possessions by other means, but let’s say you have a good base
  • autonomy: you decide for yourself which version of the consensus you want to see applied. You are truly part of the network, no one can force you to accept anything against your will

An installation still perfectible

But this installation has a drawback, it is that the key (on your Ledger and your seed) is in fact a single point of failure :

  • If the thief manages to steal the back-up of your seed, he will probably succeed in stealing your bitcoins
  • If the thief takes your Ledger and your PIN (we can imagine that he hits you on it to get it), your bitcoins are lost
  • If you lose your Ledger AND your seed, your bitcoins are lost

There is a way to limit these problems : multisignature .

As its name suggests, it is a way of accumulating several signatures to authorize a transaction. Has anyone ever seen in an American action movie from the Cold War era these scenes where you have to turn two keys simultaneously to authorize or cancel a nuclear weapon? Well Bitcoin multisig is a bit the same thing.

In general, not all signers are required to authorize a transaction, so a multisignature is often defined by the total number of signers and the number required to produce a valid transaction, e.g. 1-of-2, 2- of-3 or even 3-of-5, to name only the most frequent cases. It is a very flexible and powerful tool that allows most of the current innovations on Bitcoin, such as Lightning or sidechains , and whose possibilities we are only just beginning to exploit.

But I don’t share my bitcoins with anyone, why a multisignature?

You will surely tell me that you are the sole owner of the bitcoins , and that therefore there is no point in using several keys. Think again ! The multisig is very useful even when you are alone to protect yourself from the risk of theft and especially loss of keys.

Indeed no key is critical in an intelligently made multisig, you may have the impression of increasing your attack surface but in reality it is exactly the opposite, you remove the risk that a single error will be fatal .

Some services that offer bitcoin security are based on a multisignature with keys shared between the client, the service and possibly other actors.

Suggested 2-of-3 setup

In this tutorial, I therefore propose to set up a 2-of-3 multisig:

  1. A “hot” key that stays on your computer’s hard drive
  2. A “cold” key on your Ledger
  3. A “back-up” key in the form of a stored seed *only on paper*

The principle is as follows: of these 3 keys, only 2 are necessary to sign a transaction and spend your bitcoins. The hot key and the Ledger are used to sign your current transactions, and the “back-up” key can be imported into Electrum in the event of loss of one of the other two keys and allow the bitcoins to be moved to another address.

Please note that this is only a proposal, depending on your personal situation other schemes may be more suitable, especially if you really want to share the property with other people. But the 2-of-3 remains the most common type of multisignature and is useful in many situations, which is why I chose it for this tutorial.

Objectives of our multisig

This system protects you in the following cases:

  • If your computer is physically stolen or hacked, it is impossible to steal your bitcoins with just the hot key.
  • If your Ledger is stolen, the thief will not be able to do anything with it, even if he manages to break your PIN
  • If a thief steals your back-up, they can’t do anything with it either.

It is essential to keep a paper seed of your hot key and your Ledger, however be careful not to keep all your paper back-ups in the same place, because a thief who has access to your paper back-ups could then to take.

From now on, the loss or theft of any of these keys no longer means the loss of your savings, but keep in mind that if you lose or have 2 out of 3 keys stolen you will still lose your bitcoins!

Try to think about the conservation of your seeds, make sure that no one can have 2 keys or 2 backups out of 3 at the same time.


Setting up a multisig

So, without further ado, let’s see how!

  1. Prerequisites and equipment
  2. Generating a multisig wallet
  3. Test transaction
  4. What to do in an emergency ?
  • Prerequisites and equipment

    • Your usual computer, with Bitcoin Core, EPS and Electrum installed and configured, let’s call it “computer 1”
    • (optional) a second computer, preferably with a brand new operating system, on which you will have installed Electrum, “computer 2”
    • A Ledger already initialized with the Bitcoin app installed (see the Ledger tutorial )
    • Paper (several sheets), pencil

Why a 2nd computer? In the event that your main computer is already compromised and a hacker can find the keys on it, generating 2 of your 3 keys on this machine could allow him to steal your bitcoins. Using 2 different computers to generate 2 keys greatly reduces this risk.

  • Wallet creation

    • Generation of the “back-up” key
      • Open Electrum on computer 2 (or computer 1 if you don’t have a 2nd machine available)
      • File > New/Restore, and create a new wallet (regardless of the name)
      • Choose “Multi-signature wallet” instead of “Standard wallet”
      • You are then asked for the total number of signatories and the number required to validate a transaction. Move the first slider to 3 and the number of signatures required to 2.
      • As when creating a standard wallet, you then have to choose between the “Legacy” and “Segwit” format.

Unless you have a good reason to stay on “Legacy” addresses, I advise you to create your multisig with a native segwit address format. Whatever your choice, you must be careful that your 3 keys are of the same format, otherwise you will not be able to create your multisig!

Then note your seed on a sheet of paper, and enter your seed to confirm that it is well noted as explained in the Electrum tutorial

I advise you to write down a name to help you identify this seed (for example, “main multisig”) as well as the date of the day

Electrum then gives you a master pubkey, copy/paste it into a text document you will need it quickly

(If you are on computer 2) Find a way to send the master pubkey to computer 1. If possible avoid emails or insecure communication channels, the master pubkey is certainly less sensitive information than the private key but it remains preferable not to divulge it. If you have a password manager (you should) this might be a good way as they usually have a digital safe

      • That’s it, you can now close this window without going to the end of the process!
    • Generation of the hot key and initialization of the wallet
      • First of all, make sure you have the master pubkey of the backup key handy, especially if you used a 2nd computer to generate it
      • Open Electrum on computer 1
      • File > New/Restore, and create a new wallet
      • Choose “Multi-signature wallet” instead of “Standard wallet”
      • As in the previous step, you are then asked for the total number of signatories and the number required to validate a transaction. Move the first slider to 3 and the number of signatures required to 2.
      • Create a new seed and write it down on a sheet of paper, then confirm it as explained in the Electrum tutorial
      • Electrum then gives you a master public key (“master pubkey”), just do “next”
      • You are now asked to add your co-signers, with several options. First select “Co-sign with a hardware device” (don’t forget to plug in and unlock your Ledger!), then when asked for the 3rd co-signer “Enter a co-signer key”, and copy/paste the master pubkey of the back-up.
      • Voila, you now have a multisig wallet on Electrum!
      • Keep the 3 master pubkeys (you will find them in “Wallet > Information”), you will need them if you have to restore your wallet one day.

You can keep the master pubkeys, or find them from the seeds.

Your master pubkeys are relatively less critical information than your private keys because if a hacker were to find them, it would not allow him to steal your bitcoins. On the other hand, thanks to it, he will know all the addresses of your wallet, so this remains a big problem for your confidentiality!

Added multisig wallet in EPS

  1. If EPS is enabled, interrupt it
  2. Open the configuration file with a text editor (refer to the Electrum Personal Server guide if in doubt)
  3. Find the “multisig wallet” section, and add your own wallet, respecting the following rules:[nom de votre wallet] [espace] = [espace] [nombre de signatures requises] [espace] [master pubkey 1] [espace] [master pubkey 2] [espace] ... [master pubkey N]
  4. Save, close the text editor, and restart EPS as indicated in the tutorial. The import of new addresses will take a few minutes, and you will have to restart EPS with the same command to use it

A rescan is useless because you have not yet carried out any transaction with this wallet

  1. Test transaction

    1. Before sending all your fortune to a wallet, it is always a good idea to do a test transaction with a small amount, just to make sure everything is working as expected.
    2. As described in the Electrum tutorial, retrieve an address from the “receive” tab of your Multisig wallet and paste it into your usual wallet. Only send a small amount
    3. The transaction should instantly appear in your multisig wallet. Once confirmed, send it back to your original wallet (or any other wallet under your control).
    4. To sign a multisig transaction you need two keys, usually the one in Electrum and the one in the Ledger. So make sure the Ledger is plugged in and unlocked otherwise Electrum won’t be able to sign the transaction
    5. Everything went as planned? It’s perfect, you now have a superb multisig wallet for maximum security!
  2. What to do in an emergency ?

    1. My computer has been stolen/hacked!
      • You will need :
        • from another computer with Electrum installed
        • of your seed back-up
        • of the master pubkey of the hot key which was stolen
        • of your Ledger
      • In Electrum, launch the wallet restore with File > New/Restore
      • Choose “Multi-signature wallet”, then 2 out of 3 signatures.
      • Choose “I already have a seed”
      • Enter your seed back-up
      • Now add the hotkey master pubkey, then do “Co-sign with hardware device” (Ledger plugged in/unlocked, as always)
      • You have now restored your wallet, make a transaction without waiting to move your bitcoins to a new wallet
    2. I lost my Ledger
      • You will need :
        • from another computer with Electrum installed
        • of your seed back-up and that of the hot key
        • of the Ledger master pubkey that was stolen
      • In Electrum, launch the wallet restore with File > New/Restore
      • Choose “Multi-signature wallet”, then 2 out of 3 signatures.
      • Choose “I already have a seed”
      • Enter your seed back-up
      • In the “Add co-signers” section, select “Enter the seed of the co-signer” and then enter the seed of the hot key
      • Then add the master pubkey of the Ledger as the 3rd signer
      • You have now restored your wallet, make a transaction without waiting to move your bitcoins to a new wallet
    3. Someone got their hands on my back-up!
      • In this case, you just have to make a transaction as usual with your hot key and your Ledger to a new wallet that you will have created
    4. Hell, my computer burned down, and the same day someone stole my Ledger!
      • Do not panic ! If you still have your 3 master pubkeys and at least 2 seeds, nothing is lost!
      • You will need :
        • from another computer with Electrum installed
        • your seed back-up + at least a second seed (hot key or Ledger, it doesn’t matter)
        • Ledger’s master pubkey and hot key
      • In Electrum, launch the wallet restore with File > New/Restore
      • Choose “Multi-signature wallet”, then 2 out of 3 signatures.
      • Choose “I already have a seed”
      • Enter your seed back-up
      • In the next step, do not “Enter the co-signer’s key”, but “Enter the co-signer’s seed”, and enter a seed (that of the hot key or the Ledger, it doesn’t matter)
      • Now add the last master pubkey (note that of the seed that you did not give, for example if you entered the seed of the Ledger in the previous step, you must give here the master pubkey of the hot key
      • You have now restored your wallet, make a transaction without waiting to move your bitcoins to a new wallet

Webinar: Keeping bitcoins in cold-storage

On the program:
– The opponents of Bitcoin
– Who is Cold Storage intended for?
– Custody solutions ( custodians )
– Why not keep your Bitcoin online
– ‘Air-gapped’ and  ‘Non-Backdoor
‘ hardware – Software and Firmware verification.

How to use Bitcoin on a server?

Launch Bitcoin with the -server option, or use the daemon (bitcoind) provided in the archive to download.

Bitcoin has an interface (API) that can be used in command line or in JSON-RPC.

Mobile: what applications for Bitcoin?

There are many applications for carrying out transactions on the Bitcoin network with a mobile phone. We have tried to list them. We invite you, if necessary, to use the comments to complete this list and tell us your favorite applications as well as those that did not give you satisfaction.

It is important to distinguish, on the one hand, applications that give users complete control of their keys and the bitcoins associated with them and, on the other hand, those that are dependent on an online bank.

The SHA256 ( Secure Hash Algorithm ) checksum is created using a cryptographic hash function. Among other things, it can be used to check the integrity of a file after it has been transferred and thus ensure that the content of the file has remained unchanged on the way from the creator to the recipient of the file.

In practice, this means that changing a single character in an original file to one that has changed in many places compared to the original fileSHA-256 checksum leads. This conspicuousness can practically not be overlooked. With the current state of technology, it is not possible to change a file in such a way that an identical SHA-256 checksum is calculated despite this change.

practical guide to applying the checksum

  • A file, a text, etc. is to be transmitted or published on the Internet.
  • The creator of the file wants to ensure that a recipient of the file also receives it unchanged.
  • To do this, the creator uses a tool to generate (e.g.) an SHA-256 checksum and transmits this to the recipient together with the file or publishes it on the Internet.
  • The recipient of the file creates a new SHA-256 checksum from the received file.
  • If this sum corresponds to the sum published by the creator of the file, it can be assumed that the file was not changed on its way from the creator to the recipient.

Note on the difference between an electronic signature and a hash value ( e.g. SHA-256 checksum)

The general rule:

  • Signature = proof of person
  • Hash value / fingerprint = proof of the authenticity of a document
  • The simultaneous application of a signature and a hash value makes sense for the documents to be protected .

electronic signature

  • Documents, emails, orders, transactions, etc. can be provided with a signature. This signature is used to store a unique identifier (signature) in the document or e-mail for the person who created these documents or carried out the order, transaction, etc.
  • A signature is an ID card that can be used in the same way as a signature .
  • The signature does not encrypt a document.
  • The content of a document is not used to create a signature.
  • A signature can not be used to determine whether a document has been altered on the way to the recipient.

Hash value / SHA256 check value / fingerprint

  • A hash value is formed from the content of a document using a mathematical process .
  • A hash value says nothing about the person who created or edited the document.
  • A hash value is only used as proof of changes to a document.

SHA-256 checksum verification

The integrity of a file is checked by re-forming its SHA-256 checksum after a file has been transferred. If the SHA-256 checksum at the sender of the file is identical to that at the recipient, it can be assumed that the content of the file was not changed during transmission.

Example of different SHA-256 checksums after changing the content of a file

original content of the file:

abc d ABCD0123

SHA-256 checksum of the original file:


intentional change of the content at the 4th position from ” d ” to ” D “:

abc D ABCD0123

SHA-256 checksum of the modified file:


How to Profit from Bitcoin Forks

As much to say it right away, the vast majority of the 74 “forks” and “”airdrops” of Bitcoin currently listed will never bring you a penny. These are mostly stillborn projects that are not based on any community and are not supported by any exchange. However, some of the altcoins thus issued still find takers despite the general collapse and it is always possible to increase your bitcoin reserve a little if you manage to extract these coins in order to trade them on the markets. 

Prerequisite:  having held bitcoins at the time of the various forks on addresses for which you still have the private keys. Either May 5, 2014 for Clams , August 1, 2017 for Bitcoin Cash , October 24, 2017 for Bitcoin Gold , November 2, 2017 for Bitcore  and November 24, 2017 for Bitcoin Diamond (for the dates of the 74 “forks” ) .

Warning:  for most forks, with the exception of Bitcoin Cash,  it is currently not relevant to attempt to recover the profit from an address that contained less than 0.5 bitcoin. All platforms have a minimum threshold below which it is not possible to make trades.


The two methods indicated here are not the only ones. You can also use Bither and Bitpie  for the same result (or in addition) . Not tested also  this python script which would allow to recover the main forks. If you’ve tried these methods (or others), please let us know in the comments to this article.

1. Make sure that the address in question no longer contains bitcoins  (and never use it again to receive any). If necessary, make a transaction to another address to “empty” it. When handling private keys, the risk of theft cannot be excluded if your device is compromised.

2. Enter your public address on  in order to list the available tokens and assess their value (be careful,  does not analyze all the forks and among those considered, not all of them are recoverable).

– Only a small number of the coins presented are actually recoverable. Many of these projects have no SPV (Simple Payment Verification) wallet .
– If you go to the sites of the various projects do not download anything. Some apps may conceal malware designed to harvest and siphon off your private keys.

4. Install the Coinomi app on your smartphone  , a “multicoin” wallet for Android or IOS  that will allow you to retrieve the following forks: Bitcoin Cash (BCH), Bitcoin Gold (BTG), Bitcoin Atom (BCA), Bitcoin Private ( BTCP) and Clams (CLAM).  

5. Recover your private keys (empty of any bitcoin)
– from your paper wallets
– from an HD wallet  (also empty of any bitcoin) by extracting them when possible from your backup words .

6. On the Coinomi  app :
– install Bitcoin Cash (BCH), Bitcoin Gold (BTG), Bitcoin Atom (BCA), Bitcoin Private (BTCP) and Clams (CLAM)
forks – open the wallet of one of the forks that you have just installed
– access the menu available from the three points at the top right
– go to  “Sweep wallet” (= sweep the wallet)
– paste your private key or flash the QR Code then go to  “Next” . The app will scan the key and credit you with available coins
– repeat the operation for each of the five forks

7. Send your earnings to exchanges that accept these coins. Use for example
–  * for Bitcoin Cash (BCH/BCC) and  Bitcoin Gold (BTG),
–  * for Bitcoin Private (BTCP) and  Bitcoin Atom (BCA)
–  for Clams (CLAM)
To find a platform for each of your forks go to . Attention it is not because a coin is displayed on an exchange that deposits are necessarily possible. Service interruptions are frequent.

8. Once your keys have been emptied of all Bitcoin , Bitcoin Cash, Bitcoin Gold, Bitcoin Atom, Bitcoin Private  and Clams. You can try to recover more coins by using the “walleting” service of  which will allow you to recover coins from the following forks:  Bitcoin Diamond (BCD) United Bittcoin (UBTC), Bitcore (BTX), Segwit2X (B2X), BitcoinX (BCX), Bitcoin Faith (BTF), Bitcoin World (BTW), Bitcoin Interest (BCI), Lightning Bitcoin (LBTC), Bitcoin Pay (BTP), Big Bitcoin (BBC), Bitcoin Clean (BCL), Bitcoin God (GOD) and Bitcoin File (BIFI).
Caution: This is a centralized service  to which you will simply entrust your private keys with the risks that this implies and which will cost you 10% of the coins thus recovered . You will also need an exchange platform to provide you with a specific reception address for each coveted coin, for example:
–  * for  Bitcoin File (BIFI)
–  * for  Bitcore (BTX) , BitcoinX (BCX), Bitcoin Clean (BCL) and  Bitcoin Interest (BCI)
–  (KYC a little painful):  Bitcoin Pay (BTP) and Lightning Bitcoin (LBTC)

9. After recovering the main coins available, all you have to do is exchange them (when possible) for bitcoins and then quickly remove these funds from the various exchanges to send them to an address that you and you alone control .

A service to recover bitcoins from incomplete information

Since December and bitcoin’s rise in price, we’ve been getting regular messages from people looking to move their bitcoins – most often to an exchange – but who have only a vague idea of ​​the secret (word password, passphrase or recovery words) that would allow them to find their private keys and sign a transaction.

As much to say it immediately, the funds linked to the addresses concerned are generally lost . However, there are two exceptions to this implacable rule:
– Unblocking depends on a weak password,
– The user is able to provide information likely to greatly restrict the search field.

This is where Wallet Recovery Services comes in, which since 2013 has developed a service for brute force recovery of passwords, passphrases or recovery words, from incomplete information.

“The software basically does a brute force attack on your crypto wallet […]. Run on Linux nodes hosted on AWS, the algorithms used try a multitude of permutations of any password potentially associated with the wallet. This often works because, unfortunately, people tend to reuse the same passwords. »

Dave , one of the two co-founders, reports that the success rate is currently 35%. If successful, the service takes 20% of the bitcoins (or other cryptocurrencies) recovered.


  • Wallet Recovery Services relies entirely on trust and is therefore only to be used as a last resort , when all assumptions have been exhausted and you consider your bitcoins to be lost. The service has a good reputation (see in particular Trustpilot , Bitcointalk , Coindesk ), however we encourage you to do your own research to verify its seriousness and reliability. This is all the more important since the two co-founders remain anonymous . Before using Wallet Recovery Services you can, for example, try btcrecover , a free and open source Bitcoin wallet password recovery tool.
  • Before sending any sensitive information, contact WRS who will assess, depending on your situation, the interest of a recovery attempt.
  • It is recommended to encrypt sensitive information that you send to WRS with the PGP key indicated here to ensure that no one can intercept it.
  • WRS is not a bitcoin theft service. At the slightest doubt, we will refuse to help you.


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