[Last Call] Learn how to a build a cloud-first strategyRegister Now

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 166
  • Last Modified:

Random password generation

How do I generate a random password with 6 letters that vary in upper and lower case? I tried this code:

for ($numdigits = 1; $numdigits <= 6; $numdigits++) {
  srand(time ^ $$);
  @letters = ("a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z");
  $randnumber = rand(@letters);
  $randpassword .= $letters[$randnumber]
}

Since the seed is the time, it just generates the same random letter six times. Also, there must be a better way to do it than having an array with all of the letters...
0
chrisbolt
Asked:
chrisbolt
1 Solution
 
GunnarCommented:
You should not call srand for each iteration. Call it only once, when your program starts. If you use Perl 5.004 or later, it is not necessary to call srand() at all, as it is done automatically. (Actually, it was done automatically in older versions too, but with a bad seed.)

To avoid the letter array, generate an ASCII code between 65 and 80 (A..Z). Then, flip a coin (that is, check if rand() > 0.5); if so, add 32 (which transfers the code to the range 97..112, a..z). Example:

srand(time ^ $$);

for ($n = 1; $n <= 6; $n++) {
  $ch = 65+rand(26);
  if (rand() > 0.5) {
    $ch += 32;
  }
  $pw .= chr($ch);
}

0
 
chrisboltAuthor Commented:
Thank you, worked like a charm!
0
 
ozoCommented:
srand(time + $$) may be less likely to repeat when both time and $$ increase by one.
(or in 5.004 or later, just omit the srand, as Gunnar sugests)
seeding srand this way may also make it too easy for someone to guess what password was generated. especially if they can get a general idea of when it was generated.
And if you generate a password for one person, they may be able to figure out your clock setting by trying various seeds until they generate the same passord,
and then have a good guess about what passwords you may be generating for others.

you can also say
@letters = ('a'..'z','A'..'Z');
to initialize the array (just once, not for each itteration)
or
 $randpassword = join'',@letters[map{rand @letters}(1)x6];
to generate 6 random letters
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Tackle projects and never again get stuck behind a technical roadblock.
Join Now