Search in google this for the excel spreadsheet (BFTCalc-modified)

it should hopefully pop up

Use the Mandylion "Brute Force Attack Estimator" Excel spreadsheet (BFTCalc-modified.xls).

The length of the numbers-only password that requires at least 100 years to crack, according to the spreadsheet, is ________ characters?

Account for Moore's law. It says computing power doubles every 2 years. The spreadsheet is dated. It reflects the computing power of 4 years ago. For today, you need to quadruple its computing power assumptions. Do so by entering 4 as the "Special factor" in cell G1 (which is applied in the "computing power" cell, E24, as a multiplier). Thus, with today's computing power, the length of the numbers-only password that requires at least 100 years to crack is __________ characters.

Account for Moore's law's continued operation. If Moore's law doesn't stop, today's isn't the right computing power for the upcoming 50 years' calculations. I say that on average (less near term, more far term) that computing power is 2.5 million times todays (approximately). With that as your future computing power, the length of the number-only password that requires at least 100 years to crack is now __________ characters. (Multiply the current special factor (4) by yet a further 2500000)

If you now allow mixed random characters (spreadsheet's "PURELY Random Combo of Alpha/Numeric/Special") instead of confining your password to numerals only you should be able to use a shorter password with equal effect. The shortest "mixed character" password that'll last 100 years is __________ characters (computational power of 50 years from now).