I came up with this idea but I cant figure out if it's good or bad, maybe you can help. My goal is: I want to create extremely strong passwords for my main accounts (gmail, skype and so on). I want to have different passwords for all my accounts that are longer than 20 characters and that contains lower+upper case chars, numbers and special characters. What would you do to achieve that?
It's pretty impossibile to remember even one password like that so I came up with this idea: what if I develop a (simple and secret) hashing algorithm that transforms easy passwords (even 3 or 4 characters) into strong ones?
In that scenario I would only have to remember "dog" for my Gmail, "black" for Yahoo and so on. When you have to login, you just process your easy password in your handmade script that converts it, than you just copy-paste.
I think this method is great for some reasons:
if your hashing algo is irreversible and secret, there's no way to figure out the "easy passwords" by having (even a lot) of the strong passwords (anyway you must be really unlucky if someone managed to hack all your main accounts on gmail, forums, instant messaging and so on)
i just have to remember extremely easy words for all my accounts while my "final passwords" will be bulletproof for lots of years
if well made, an easy hashing algo can just be remembered and used on paper instead of making a script (that could be eventually stolen). the algorithm can be easy because you dont need an extremely good avalanche effect (you won't be making tens of thousands of passwords, maybe just 100 or 200 in a few years?
Even if a cracker managed to understand the formulas in your hashing algorithm, there are no public rainbow tables for your algorithm, and I highly doubt that your gmail account is so valuable that anyone would start making one. This method is meant only for everyday passwords, not for high risk situations where NSA is involved, and it is good because the algoritm is related only to YOUR passwords, because it's not a public one. MD5 is used by thousands of websites, that's why people started wasting time/money to crack it. My personal algo will be just mine, so noone will be interested to invest money to crack it
What's your opinion?
PS. sorry of my extremely bad english :)