Passwords, Passwords and Passwords. Everyone keep stressing on choosing good passwords. I think each and every person who have even a little bit of knowledge of computers and internet do have at least 3 or 4 passwords at least for various accounts.
So, why one should have a strong passwords? Actually, passwords are the keys to access personal information. Be it mails, Facebook account, Orkut account and the most important, bank account. It the password which is a barrier between your data and the one who can accesses it illegally i.e passwords are the guards or locks who restrict illegitimate access to your personal and sensitive information. If the guards and locks are strong only then they will be able to secure your information. Therefore, one should always have strong passwords.
Now coming to next question, what is a strong password or how a strong password look like.
You must have heard that the strong passwords are those that are long. Even banks and many websites force users to have passwords with a minimum length like 8 characters. In my opinion, passwords with length 12 are very strong. Further, if your password is a combination of digits, alphabets and special symbols then it makes password very very strong. In short, the greater the length and variety of characters in your password, the harder it is to guess and this is a strong password. There are programs who can do a this guess work at a very high speed and accuracy. And, complex passwords which are difficult to guess are the key.
Complexity of the passwords depends primarily on its length and the combination of characters which are used. Now, let us use simple mathematics to see how above factors make a password complex. Of course you don’t have to follow mathematics for choosing passwords. This is just for understanding how a combination of characters makes password complex and hence secure too.
First of all we’ll cover a very very simple case for our understanding. Suppose, I want to create a password of two characters with a restriction that I should use only two digits, 1 and 3. So, how many passwords will I be able to create? Well, not difficult to guess. So, no prize for this 
. Below are the combinations
Position 1 Position 2
1 3
1 1
3 1
3 3
The total number of combinations comes out to be 4.
In other words, if we have 2 digits and want to create password with length 2 then we can fill the first position(Position 1 ) with 2 characters(1 or 3) and second position (Position 2) also with 2 characters(1 or 3). Below is the same.
Position 1 Position 2
No. of possible entries 2 2
From above chart, Total number of resulting combinations or possible passwords would be equal to 2 * 2 which is equal to 4 and my password would be one of these 4 combinations.
Now, let us take one more example. If I want to make a password of length 2 by using digits 1, 3 and 5 then how many possible passwords can be created. Both, position 1 and Position 2 can be filled with three possible digits(1, 3 or 5). Below is the resulting chart.
Position 1 Position 2
No. of possible entries 3 3
So, total no. of possible passwords = 3 * 3 = 9. Something for you to work upon. Just try to enumerate all the combinations. It’ll come out to be 9 only.
From above two cases it is quite clear that if someone wants to guess your password then he/she have to try 4 and 9 combinations respectively and your password must be one of the combination. Easy
So, what we learned till now? It is :
Total number of resulting combinations or possible passwords for a specified length is always EQUAL to the multiplication of the No. of possible entries at various positions. And, it is the total number of possible combination which makes a password complex or difficult to guess.
So, we know the basic formula of how to calculate possible number of combinations or passwords.
Now we will see why it is always recommended to use a combination of alphabets, digits and special characters with length, say 10, to get a strong password.
I am using an English keyboard and below is the number of characters on the keyboard.
Digits = 0 to 9 (10)
Alphabets = A to Z (26) + a to z (26) = 42 (remember that capital and small letters are considered different in passwords)
Special characters = 32 (just count on your keyboard)
So, if a password is a combination of alphabets, digits and special characters then each of the positions can be filled with either digits which are 10 in number or alphabets which are 42 in number or special characters which are 32 in number. Which means,
Number of possible entries at each position would be 10+42+32 = 84 i.e
Positions 1 2 3 ………………………… 10
No. of possible entries 84 84 84 84
Since length of our password is 10 therefore total number of possible passwords or combinations would be 84*84*84*84*…… ten timesand the result comes out to be 17490122876598091776 which no doubt is BIG number and your password is one of these many combination. Wow! quite difficult to guess your password out of these many.
Some tips for choosing passwords :
1) First of all use combination of letters, digits and special characters.
2) Avoid using your login name, part of your name, birthday or similar information.
3) Avoid dictionary words. Now a days there area sophisticated tools that can rapidly guess passwords which are based on words in dictionaries including words spelled backwards, common misspelling etc. Such words will defy the purpose of step 1 because the cracking tool will guess the obvious dictionary word thereby reducing the remaining possible number of combinations.
I hope now you know what kind of difference a combination of various characters can make in terms of increasing the complexity of a password.
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