There is more to a bitcoin wallet than just the address itself. It also contains the public and private key for each of your bitcoin addresses. Your bitcoin private key is a randomly generated string (numbers and letters), allowing bitcoins to be spent. A private key is always mathematically related to the bitcoin wallet address, but is impossible to reverse engineer thanks to a strong encryption code base.

1. Generate Bitcoin Address From Public Key Converter
2. Generate Bitcoin Address From Public Key System
3. Create Bitcoin Address

A Bitcoin wallet is where you store your bitcoins. Technically it is a collection of private keys which may be owned by you or someone with the permission to manage those keys and to make transactions on the Bitcoin network. Wallets maybe online. The public and private keys in a Bitcoin address are a normal ECDSA key pair. I haven't poked through this particular bit of Bitcoin's own code but the offshoot products I've had a chance to work with typically use the Bouncy Castle crypto library. Jul 16, 2018 How to create a Bitcoin wallet address from a private key Elliptic Curve Cryptography. The first thing we need to do is to apply the ECDSA or Elliptic Curve. Once we’re done with the ECDSA, all we need to do is to add the bytes 0x04 at. Compressed public key. But we can do better. You see, to create a public key from a private one, Bitcoin uses the ECDSA, or Elliptic Curve Digital Signature Algorithm. More specifically, it uses one particular curve called secp256k1. Now, this curve has an order of 256 bits, takes 256 bits as input, and outputs 256-bit integers.

If you don’t back up your private key and you lose it, you can no longer access your bitcoin wallet to spend funds.

As mentioned, there is also a public key. This causes some confusion, as some people assume that a bitcoin wallet address and the public key are the same. That is not the case, but they are mathematically related. A bitcoin wallet address is a hashed version of your public key.

Every public key is 256 bits long — sorry, this is mathematical stuff — and the final hash (your wallet address) is 160 bits long. The public key is used to ensure you are the owner of an address that can receive funds. The public key is also mathematically derived from your private key, but using reverse mathematics to derive the private key would take the world’s most powerful supercomputer many trillion years to crack.

Besides these key pairs and a bitcoin wallet address, your bitcoin wallet also stores a separate log of all of your incoming and outgoing transactions. Every transaction linked to your address will be stored by the bitcoin wallet to give users an overview of their spending and receiving habits.

Last but not least, a bitcoin wallet also stores your user preferences. However, these preferences depend on which wallet type you’re using and on which platform. The Bitcoin Core client, for example, has very few preferences to tinker around with, making it less confusing for novice users to get the hang of it.

Your bitcoin wallet generates a “master” file where all of the preceding details are saved. For computer users, that file is called wallet.dat. It’s saved on a Windows machine, for example, in the C:UserYournameDocumentsAppDataRoamingBitcoinfolder. Make sure to create one or multiple backups of this wallet.dat file on other storage devices, such as a USB stick or memory card. The bitcoin wallet software will let you import a wallet.dat file in case your previous file is damaged or lost, restoring your previous settings, including any funds associated with your bitcoin wallet address.

Check out more information on importing private keys and wallet.dat files.

In the previous article, we looked at different methods to generate a private key. Whatever method you choose, you’ll end up with 32 bytes of data. Here’s the one that we got at the end of that article:

60cf347dbc59d31c1358c8e5cf5e45b822ab85b79cb32a9f3d98184779a9efc2

We’ll use this private key throughout the article to derive both a public key and the address for the Bitcoin wallet.

What we want to do is to apply a series of conversions to the private key to get a public key and then a wallet address. Most of these conversions are called hash functions. These hash functions are one-way conversions that can’t be reversed. We won’t go to the mechanics of the functions themselves — there are plenty of great articles that cover that. Instead, we will look at how using these functions in the correct order can lead you to the Bitcoin wallet address that you can use.

Elliptic Curve Cryptography

The first thing we need to do is to apply the ECDSA or Elliptic Curve Digital Signature Algorithm to our private key. An elliptic curve is a curve defined by the equation y² = x³ + ax + b with a chosen a and b. There is a whole family of such curves that are widely known and used. Bitcoin uses the secp256k1 curve. If you want to learn more about Elliptic Curve Cryptography, I’ll refer you to this article.

By applying the ECDSA to the private key, we get a 64-byte integer. This consists of two 32-byte integers that represent the X and Y of the point on the elliptic curve, concatenated together.

For our example, we got: 1e7bcc70c72770dbb72fea022e8a6d07f814d2ebe4de9ae3f7af75bf706902a7b73ff919898c836396a6b0c96812c3213b99372050853bd1678da0ead14487d7.

In Python, it would look like this:

Note: as you can see from the code, before I used a method from the ecdsa module, I decoded the private key using codecs. This is relevant more to the Python and less to the algorithm itself, but I will explain what are we doing here to remove possible confusion.

In Python, there are at least two classes that can keep the private and public keys: “str” and “bytes”. The first is a string and the second is a byte array. Cryptographic methods in Python work with a “bytes” class, taking it as input and returning it as the result.

Now, there’s a little catch: a string, say, 4f3c does not equal the byte array 4f3c, it equals the byte array with two elements, O&lt;. And that’s what codecs.decode method does: it converts a string into a byte array. That will be the same for all cryptographic manipulations that we’ll do in this article.

Public key

Once we’re done with the ECDSA, all we need to do is to add the bytes 0x04 at the start of our public key. The result is a Bitcoin full public key, which is equal to: 041e7bcc70c72770dbb72fea022e8a6d07f814d2ebe4de9ae3f7af75bf706902a7b73ff919898c836396a6b0c96812c3213b99372050853bd1678da0ead14487d7 for us.

Compressed public key

But we can do better. As you might remember, the public key is some point (X, Y) on the curve. We know the curve, and for each X there are only two Ys that define the point which lies on that curve. So why keep Y? Instead, let’s keep X and the sign of Y. Later, we can derive Y from that if needed.

The specifics are as follows: we take X from the ECDSA public key. Now, we add the 0x02 if the last byte of Y is even, and the byte 0x03 if the last byte is odd.

In our case, the last byte is odd, so we add 0x03 to get the compressed public key: 031e7bcc70c72770dbb72fea022e8a6d07f814d2ebe4de9ae3f7af75bf706902a7. This key contains the same information, but it’s almost twice as short as the uncompressed key. Cool!

Previously, wallet software used long, full versions of public keys, but now most of it has switched to compressed keys.

Encrypting the public key

From now on, we need to make a wallet address. Whatever method of getting the public key you choose, it goes through the same procedure. Obviously, the addresses will differ. In this article, we will go with the compressed version.

What we need to do here is to apply SHA-256 to the public key, and then apply RIPEMD-160 to the result. The order is important.

SHA-256 and RIPEMD-160 are two hash functions, and again, we won’t go into the details of how they work. What matters is that now we have 160-bit integer, which will be used for further modifications. Let’s call that an encrypted public key. For our example, the encrypted public key is 453233600a96384bb8d73d400984117ac84d7e8b.

Here’s how we encrypt the public key in Python:

Adding the network byte

The Bitcoin has two networks, main and test. The main network is the network that all people use to transfer the coins. The test network was created — you guessed it — to test new features and software.

We want to generate an address to use it on the mainnet, so we need to add 0x00 bytes to the encrypted public key. The result is 00453233600a96384bb8d73d400984117ac84d7e8b. For the testnet, that would be 0x6f bytes.

Checksum

Now we need to calculate the checksum of our mainnet key. The idea of checksum is to make sure that the data (in our case, the key) wasn’t corrupted during transmission. The wallet software should look at the checksum and mark the address as invalid if the checksum mismatches.

You can find it in these two articles:.If you need a Java license key manager for your software applications, True License is a good, open source solution, and with these two articles, you should be able to implement True License easier than ever before. Generate unique license keys for each sale of people. If you haven't heard of it before, the Java Store 'is an application storefront that provides an easy and secure way to discover Java applications for your desktop.' Java Store updateIn a related note, the ' is still in beta. Using True License as a Java license key manager - UpdateOkay, I've finally gotten around to releasing my True License client and server code. I don't know what they're doing for software licensing and license management, but I thought I'd mention this 'store' again here today.

To calculate the checksum of the key, we need to apply SHA-256 twice and then take first 4 bytes of the result. For our example, the double SHA-256 is 512f43c48517a75e58a7ec4c554ecd1a8f9603c891b46325006abf39c5c6b995 and therefore the checksum is 512f43c4 (note that 4 bytes is 8 hex digits).

The code to calculate an address checksum is the following:

Getting the address

Finally, to make an address, we just concatenate the mainnet key and the checksum. That makes it 00453233600a96384bb8d73d400984117ac84d7e8b512f43c4 for our example.

That’s it! That’s the wallet address for the private key at the start of the article.

Generate Bitcoin Address From Public Key Converter

But you may notice that something is off. You’ve probably seen a handful of Bitcoin addresses and they didn’t look like that. Well, the reason is that they are encoded with Base58. It’s a little bit odd.

Here’s the algorithm to convert a hex address to the Base58 address:

What we get is 17JsmEygbbEUEpvt4PFtYaTeSqfb9ki1F1, a compressed Bitcoin wallet address.

Conclusion

The wallet key generation process can be split into four steps:

• creating a public key with ECDSA
• encrypting the key with SHA-256 and RIPEMD-160
• calculating the checksum with double SHA-256
• encoding the key with Base58.

Depending on the form of public key (full or compressed), we get different addresses, but both are perfectly valid.

Generate Bitcoin Address From Public Key System

Here’s the full algorithm for the uncompressed public key:

If you want to play with the code, I published it to the Github repository.

I am making a course on cryptocurrencies here on freeCodeCamp News. The first part is a detailed description of the blockchain.

Create Bitcoin Address

I also post random thoughts about crypto on Twitter, so you might want to check it out.