If you're tired of the random addresses generated by regular Bitcoin clients, you can use a vanity address program to create a more personalized address. For example, you could create an address that starts '1Satoshi' and ask people to send Bitcoin to 1SatoshiHHqnDPRSfiZ5GXJ8Gk9dbjO.
Vanity address programs accept as input a pattern (e.g. 1Bitcoin) and create a public address and private key. The amount of time required to find a given pattern depends on how complex the pattern is, the speed of the computer, whether it is using CPU or GPU, and if you get lucky.
|1QLbz6||259,627,881||This vanity is alphabetically located before a major pivot, the RIPEMD160 hash value of 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF (address: 1QLbz7JHiBTspS962RLKV8GndWFwi5j6Qr).|
|1QLbz7||837,596,142||This vanity is partially after a pivot and thus the difficulty increases.|
|1QLbz7JHiBTspS962RLKV8GndWG||1.6489E+47||After a major pivot and 59 times as difficult as the 'E' vanity.|
|1aaaaa||15,318,045,009||After various pivots and subsequently more difficult.|
|1abcdef||888,446,610,539||Six characters case sensitive starting with a lower case character.|
|111111||1,099,511,627,776||A special case: leading number 1 (one) is especially difficult.|
|1abcdefg||51,529,903,411,245||Seven characters case sensitive starting with a lower case character.|
|1abcdefgh||2,988,734,397,852,220||Eight characters case sensitive starting with a lower case character.|
You might think that you would be able to find the private key for a given address by running a vanity address generator. In practice, this is considered impossible. Given that the difficulty increases exponentially the longer your vanity is, so does the average time required to find that vanity. The table below shows how an increasingly complex vanity affects the difficulty and average time required to find a match only for that vanity, let alone the full address, for a machine capable of looking through one million keys per second.
|1Bitc||4,476,342 (4.48E+6)||< 10s|
|1Bitco||259,627,881 (2.6E+8)||3 minutes|
|1Bitcoi||15,058,417,127 (1.506E+10)||3 hours|
|1BitcoinEaterAddressDontSend||1.6209E+47||3.3E+33 or 3.3 decillion years.|