bitcoin addresses

[mico]

Why all addresses in my addressbook start with '1' ?

[FreeMoney]

Why all addresses in my addressbook start with '1' ?

All addresses start with 1, it gives them a bit of form, not just any clump of characters can be a bitcoin address.

[Gavin Andresen]

Because the first byte in a bitcoin address is a version number, and "version 0" is encoded as a "1" in the bitcoin address "base58 encoding" (because 0 is too easy to confuse with capital-o).

Trivia:  -testnet addresses are version 111 (eleven is my favorite number), and begin with m or n (I haven't actually worked out whether they might begin with another letter, too...).

[Hal]

Satoshi once suggested that people could hack their client to generate and discard a bunch of random addresses until you got one that started with your initials or even your name if it was short. Well, I guess it would have to skip the forbidden letters like 'l'.

Signed, Ha.

[Gavin Andresen]

Satoshi once suggested that people could hack their client to generate and discard a bunch of random addresses until you got one that started with your initials or even your name if it was short.

I wrote a 'vanity bitcoin address' patch a while ago that lets you do exactly that:  https://gist.github.com/614460

I bet finding an address starting  1HAL...  wouldn't take more than a few hours.  If I recall, it took a day or so to find one with the string 'gavin' in it.