|
Title: What is the probability of a bitcoin address starting with "11..." ? Post by: schnuber on May 14, 2016, 08:11:58 PM Hi
This is not a very important question that some statistics geeks of you probably may answer easily. I wonder because I am currently writing code that creates a bitcoin address, and this question just occurred to me. Greets Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: vlamer on May 14, 2016, 09:40:53 PM can i answer this question with yes or no ;D
maybe this can explain your question https://en.bitcoin.it/wiki/Vanitygen (https://en.bitcoin.it/wiki/Vanitygen) , because I also just learned from there. Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: hhanh00 on May 15, 2016, 02:38:28 AM The first 1 comes from the address version and is always there for a normal bitcoin address. Every other 1 requires a byte equal to 0 is the pub key hash.
- 11: 1/2^8 = 1/256 - 111: 1/2^16 = 1/65536 - 1111: 1/2^24 etc Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: jl777 on May 15, 2016, 03:41:06 AM The first 1 comes from the address version and is always there for a normal bitcoin address. Every other 1 requires a byte equal to 0 is the pub key hash. are you sure?- 11: 1/2^8 = 1/256 - 111: 1/2^16 = 1/65536 - 1111: 1/2^24 etc It seems base58 would have a 1/58th chance for a '1' Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: 2c0de on May 15, 2016, 08:47:02 AM 1/58
about 1.7% Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: amaclin on May 15, 2016, 09:06:16 AM are you sure? There are no bitcoin addresses starting with "1Z...", "1Y..." It seems base58 would have a 1/58th chance for a '1' The formula for probability is more complicated Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: hhanh00 on May 15, 2016, 09:42:58 AM 1/58 about 1.7% That can't be this simple since 100% of the p2kh addresses begin with 1 ;) Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: shorena on May 15, 2016, 07:58:47 PM are you sure? There are no bitcoin addresses starting with "1Z...", "1Y..." It seems base58 would have a 1/58th chance for a '1' The formula for probability is more complicated No? Code: Address: 1ZXt58NWzZaGxmdcYBccLJL2WNQrTqhuR For a reference that hhanh00 is correct, see the footnote (marked with *), here[1] [1] https://en.bitcoin.it/w/images/en/9/9b/PubKeyToAddr.png Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: amaclin on May 15, 2016, 08:04:20 PM Oups. Sorry.
There are no 35-character long (this is most popular length for standard address) addresses starting with "1Z...", "1Y..." The probability to generate such address is less than 1/58 So, the probability for others is not 1/58 :D Title: Re: What is the probability of a bitcoin address starting with "11..." ? Post by: deepceleron on May 16, 2016, 03:35:12 PM The first 1 comes from the address version and is always there for a normal bitcoin address. Every other 1 requires a byte equal to 0 is the pub key hash. are you sure?- 11: 1/2^8 = 1/256 - 111: 1/2^16 = 1/65536 - 1111: 1/2^24 etc It seems base58 would have a 1/58th chance for a '1' Base58 conversion always preserves leading 0 bytes by directly encoding them as a "1" at the start of an address. This is the reason all standard Bitcoin addresses start with 1, because of the hard-coded network ID byte of 00 for Bitcoin. A byte can store a value 0-255; the chance that the next byte (the first digit of the hash) is also 0x00h is 1 in 256, and so on. The Bitcoin address in it's native binary form (that you never see) is 25 bytes, it's parts are: byte 0: Network ID Byte (0x00 for main bitcoin network) byte 1-20: ripemd160 hash (20 bytes) of sha256 hash (32 bytes) of 0x04+public key (65 bytes) byte 21-24: checksum: first four bytes of sha256 hash of sha256 hash of bytes 0-20 above Only after the leading byte preservation is the address then put through Base58-encoding. The other non-related "answers" seen in this thread are also wrong: because the largest Bitcoin address (all FFFFs for the hash plus checksum) is 1QLbz7JHiBTspS962RLKV8GndWFwi5j6Qr, there are strange address probabilities. The chance of an address starting with characters 12 - 1P is about 1-in-23; an address starting 1R-1z must be a 33 character or less address, and chances are 1-in-1353. As we now know, starting in 11 is 1-in-256. |