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Does it mean the shorter a address,easier to generate it?Will it be less secure?
Yes, shorter addresses are easier to find, but the security is the same. It would be easier for someone else to create an address that also starts with 1siroh, but the rest would not be the same thus its a different address with the same beginning.
i was also trying to generate a unique bitcoin address. but after nearly 6 days of non-stop letting my pc run, i stopped it. it's just not worth the time.
The longer the pattern the longer the time it will take to search - if you're lucky... it might take only 2 seconds. Anyway, I would suggest you to buy a a VPS from Time4VPS and run vanitygen on them. My computer was running at
350 MKeys per seconds and the VPS I used was running at 500 MKeys per seconds. It took me around 4 hours to generate the address 1
JTKingdNGmCfbP8HCbhenoxRQuy8tqZvs (without -i option).
What hardware do you use for 350Mkey/s? Are you sure its million keys per second? because at 37M(!)keys/s it took me a few minutes to get 1JTKingnFGyKqoFvztGVngqpw2qndA6qW5.
My i5 does ~700Kkeys/s and would take ~4.1h for 50% chance, so I guess you used a CPU as well.