Bitcoin Forum

Hello does anyone knows how reedem casascius Bitcoin?

If your casascius coin has a sticker on the back with a mini private key you can redeem it with Electrum.
You can download Electrum wallet from https://electrum.org/

And then use this format below when importing the mini private key

You'll have to remove the prefix "p2pkh:".
For some reason, adding a prefix before a mini-private key will disable the "next" or "sweep" in Electrum's import or sweep private key.

You can find more detailed information here: https://en.bitcoin.it/wiki/Mini_private_key_format

When you want to sweep or import a mini private key, Electrum will convert it to a full-size private key and generate a "p2pkh" address from it by default.
https://github.com/spesmilo/electrum/blob/07219cc4c6435011afacda546f652cea91d98cd4/electrum/bitcoin.py#L666

One of the conditions for Electrum to recognize a private key as a valid mini key is that its first character must be an "S". If you add p2pkh in front of it the "text[0] == 'S'" condition will fail and the next button will remain disabled.

Thanks, without looking at the code, my initial guess was: it's because of the checksum: SHA256(mini-privKey + ?) =  0x00 first byte; and it includes the "p2pkh:" to hash.
Pretty close but it's the last (third) 'condition'.

So they've also included to check for "S" as the first character of what's actually pasted there.

Can you explain the difference between the Mini Private key and the Full-size Private key? Is this something like a URL shortener where you make it easier for people to remember the Private Key?

I have swept many Private keys into Electrum from my Paper wallets, but I have never seen this before. OP ..thank you for posting this, I learn something new every day.  ;)

Almost any integer between 1 and 2²⁵⁶ can be turned into a full-size private key. A big difference of mini private keys with other formats is that, not every 256-bit number that can be encoded in a full-size private key can be encoded in mini private key format too.
The other difference I know is that there is no way to convert other formats of private keys to a mini private key.


A mini private key (even the shortest format which includes 22 characters) is still difficult to be memorized.
A mini private key can be used when there is no enough space for writing a full-size private key.

Keep in mind that mini-private keys represent a smaller "entropy" size that is used to derive the 256-bit key. The algorithm is that they start from a 256-bit number then shrink the string representation of it to smaller number of characters (eg. 30) and this final string acts as the input to SHA256 to get the 256-bit key.