address formats -- what do they mean?

[birr]

Bugs me it's kind of hard to get basic facts about bitcoin.
Example:  I recently saw a mention of "sipa" addresses, which I've never heard of.
This was in a thread explaining how to use Mycelium.
The writer didn't explain sipa addresses.

Developers, and really anybody who writes about bitcoin in the context of explaining it to newcomers and making it more widely available, need to keep in mind:
most people do not come to bitcoin knowing these things

I did quite a bit of searching forums and googling, trying to research sipa, to little avail.
On my own, I ferreted out some basic facts about addresses, to show that I did some work, and make this post more legitimate.  Because I wasn't able to get very far, persons with more knowledge than I are invited to continue the thread by explaining sipa addresses in a way that beginners can understand.

A bitcoin address has 160 bits.
The commonest, uncompressed address format uses base58 and comprises 34 characters, the first of which is always 1, which leaves 33 characters to convey information.  I believe this is "WIF," but correct me if I'm wrong.
Base58 requires 28 characters to hold 160 bits.  This leaves five characters for a checksum, or some sort of error prevention, which is why, in this format, you don't have to worry about a typo resulting in btc going to the wrong address.

A sipa address looks like this
14TYdpodQQDKVgvUUcpaMzjJwhQ4KYsipa
You can paste that into the search box at blockchain.info; it is a valid address.
Like WIF, sipa has 34 characters, and the first character always 1; but the last four characters are always sipa.  This leaves 29 characters to hold 160 bits of information -- only one extra character above the 28 required.
I went to blockchain.info to see what would happen if a sipa address was entered with a typo.  It didn't accept it.

That's as far as I got, trying to find out what sipa means.
Ok guys, start at the beginning, and please keep it simple.

[1714944283]

1714944283

[1714944283]

1714944283

[1714944283]

1714944283

[odolvlobo]

As far as I know, there is no such thing as a "sipa" address. 14TYdpodQQDKVgvUUcpaMzjJwhQ4KYsipa is a standard bitcoin address apparently owned by bitcoin.sipa.be, which is a site that publishes difficulty graphs.

The bitcoin wiki (https://en.bitcoin.it/wiki/Main_Page) is a good source of Bitcoin information. For example:

Wallet import format: https://en.bitcoin.it/wiki/WIF
Technical background of version 1 Bitcoin addresses: https://en.bitcoin.it/wiki/Technical_background_of_Bitcoin_addresses

[Cryddit]

http://en.wikipedia.org/wiki/Securities_Investor_Protection_Act

May be relevant, if they were talking about moving money around outside of the bitcoin system.

Those four letters though don't mean anything in particular in the context of a bitcoin address.

[TippingPoint]

Base58Check encoding

https://en.bitcoin.it/wiki/Base58Check_encoding

[birr]

Thanks for the replies.  It's still kind of a mystery to me how and why someone fabricates an address with that special suffix.  Has something to do with the Securities Investor Protection Act.  But what's the story there, and what is bitcoin.sipa.be?
https://blockchain.info/address/14TYdpodQQDKVgvUUcpaMzjJwhQ4KYsipa

[klabaki]

Thanks for the replies.  It's still kind of a mystery to me how and why someone fabricates an address with that special suffix.  Has something to do with the Securities Investor Protection Act.  But what's the story there, and what is bitcoin.sipa.be?
https://blockchain.info/address/14TYdpodQQDKVgvUUcpaMzjJwhQ4KYsipa

How are these addresses created?

--> It's called "vanity address": You simply create and forget new addresses until you find an address that you like, i.e. with a special prefix or suffix. In this case new addresses were generated until one with the suffix "-sipa" was found.

Who is "sipa"?

--> One of the core developers. Involved in Bitcoin since ancient times.

[kellrobinson]

Who is "sipa"?
--> One of the core developers. Involved in Bitcoin since ancient times.

Trying to be funny?
If you don't mind, let's get the discussion back on track.
Entering a valid sipa address in blockchain.info takes you to a different site (sipa.be) than entering an ordinary vanity address would take you.  There may be more to this than a vanity address with "sipa" in it.
I think clearly there is a sipa format, I found a mention of it near the bottom of this post by cetus
https://bitcointalk.org/index.php?topic=293472.msg5605110#msg5605110
"The SIPA format for private keys includes the compression flag."
Anybody have more info about this?

[klabaki]

Trying to be funny?
If you don't mind, let's get the discussion back on track.

The discussion never lost track. Apparently, birr didn't know about sipa, the developer, and therefore said some fuzz about "Securities Investor Protection Act". This was kinda funny to me, so I laughed while explaining it.

Entering a valid sipa address in blockchain.info takes you to a different site (sipa.be) than entering an ordinary vanity address would take you.  There may be more to this than a vanity address with "sipa" in it.

Blockchain.info provides additional services than just viewing the blockchain: They also allow people to make a sticky note to an address, linking to a website of the user's choice. Apparently, this address has been linked to sipa's homepage.

I think clearly there is a sipa format, I found a mention of it near the bottom of this post by cetus
https://bitcointalk.org/index.php?topic=293472.msg5605110#msg5605110
"The SIPA format for private keys includes the compression flag."
Anybody have more info about this?

You are mixing up "address format" and "private key format".

The private key format is commonly known as "wallet import format", and is best described on it's wiki page:

https://en.bitcoin.it/wiki/Wallet_import_format

One thing that is not mentioned on the wiki page is that a different prefix is used in place of 0x80 to indicate a compressed pubkey.

[flatfly]

The "sipa" format is simply another name for what is commonly referred to as WIF -
the standard human-readable representation for bitcoin private keys.

The wiki is usually a good source of information for this type of thing.