Create an uncompressed public address from a compressed public address

[nkotb0]

An old friend of mine, J-P, created a bitcoin wallet a long time ago.
The public compressed address of this wallet is 1FYPDCP1uVnPgEE3gaDMbAApdv9XYX7Si5
I need uncompressed public address now, could someone generate this ?
Thank you so much.

I’m a big Bitcoin fan ... and I recently started learning about bitcoin, private and public keys, elliptic curves, python programming, etc.

P.S: I would like to respect my friend's privacy, so please provide me a private contact if you could generate this. Thanks.

New Kid On The Block

[elda34b]

P.S: I would like to respect my friend's privacy, so please provide me a private contact if you could generate this. Thanks.

Is there a reason why you need his uncompressed address? Why not ask him directly instead of asking some random stranger on the internet, and telling them your friend address?

If you want to learn how to do it, there's no need to use your friend address btw, you can just create your own address.

[nkotb0]

I have a good reason for that, please believe me.

[BlackHatCoiner]

I need uncompressed public address now, could someone generate this ?

If someone could generate an uncompressed address or the specific address you wrote?

If it's the first one, then yes, you can still generate uncompressed addresses, it's just not recommended. Instead of hashing the compressed public key in the step 2, hash the uncompressed public key.

For example, take this public key:

Code:

02817c2e406a127b429cdd69f3f7980fdaf9d50d69ca17ba05510dc2d7d8b49057

The starting “02” means that your y is an even number. Solve the equation: y² = x³ + 7 and you get:

Code:

x = 817c2e406a127b429cdd69f3f7980fdaf9d50d69ca17ba05510dc2d7d8b49057 
y = 4af04f9a650a6c1475a2722abde70ace45426054155dd1f5af7fcdf5e8bd8e42

Your uncompressed public key will be “04” + x + y.

Thus, we have:

Code:

04817c2e406a127b429cdd69f3f7980fdaf9d50d69ca17ba05510dc2d7d8b490574af04f9a650a6c1475a2722abde70ace45426054155dd1f5af7fcdf5e8bd8e42

Hash it with SHA256 and continue the steps by yourself. This uncompressed public key gives us:

Code:

13V9JCQ2WhFp2vkKadeuydVg4heHptQNPo

If you meant the specific address, then it's impossible. (for you to generate what he did)

[NotATether]

You cannot convert between compressed and uncompressed addresses and vice versa, you need the public key of the address to generate the (un)compressed versions of addresses. This can be obtained either from a block explorer (requires a sending transaction from the address) or from its private key.

[nkotb0]

If I understand correctly then in the current situation it is not possible to find out what the other address is.
Thank you for your help.

[ranochigo]

Bitaddress does this for you, if you don't want to hassle yourself with the headaches if you do it incorrectly. You'll have to get the correct WIF as well, by the way.

Download the github repo: https://github.com/pointbiz/bitaddress.org. Validate it with the PGP signature file and open the HTML with your browser. Go to Wallet Details and Enter your private keys > View details. You should see both uncompressed and compressed addresses derived from the priv key. Run it on a clean computer with a clean browser (ie. no extensions).

If I understand correctly then in the current situation it is not possible to find out what the other address is.

No if you don't have your private key or ECDSA public key.

[BitMaxz]

Alternative for ranochigo above you can use this tool https://iancoleman.io/bitcoin-key-compression/

Just paste the private key and it will generate both compressed and uncompressed Bitcoin addresses or if you have a public key(Hex encoded) you can also use that to create compressed and uncompressed public keys using the tool above.

Just make sure that you download the page and run it offline for safety purposes except if you have the hex-encoded public key.