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How to encrypt and decrypt password in php

29 New Member
can i ask
how to encrypt an password in php code?
then how to decrpty it after encrypt?

thanks
Aug 17 '09 #1
19 39960
code green
1,726 Recognized Expert Top Contributor
To do this you need to write your own encrypting algorithm.
The system supplied functions sha_1 and md5 are "un-decryptable".
This all makes sense really because if there were publicly available functions that encrypted and decrypted it would make them fairly useless.
Aug 17 '09 #2
unauthorized
81 New Member
The PHP's OpenSSL interface has everything you may ever want from encryption/decryption/hashing and even an awsome RNG.

See php.net/openssl
Aug 17 '09 #3
Dheeraj Joshi
1,123 Recognized Expert Top Contributor
Basically... Do md5 on the password for encryption..

But 50% of worlds password are "password", so doing on the frequency analysis one can guess the password.(Thoug h it require some work).

So you better to add some salt(string of random characters 16characters or 8 characters) for password of each user.

So now md5 the password and salt and then validate it against database.

So even if the passwords for various users are same your salt(unique for each user) make the passwords different.(So no same patterns in the database basically).

For validating

Take password from user and for his username fetch the salt.
do md5 on both of them and check against the database.

Expand|Select|Wrap|Line Numbers
  1. <?php
  2.  
  3. $len = 16;
  4.  
  5. $base='ABCDEFGHKLMNOPQRSTWXYZabcdefghjkmnpqrstwxyz123456789';
  6.  
  7. $max=strlen($base)-1;
  8.  
  9. $activatecode='';
  10.  
  11. mt_srand((double)microtime()*1000000);
  12.  
  13. while (strlen($activatecode)<$len+1)
  14.  
  15.   $activatecode.=$base{mt_rand(0,$max)};
  16.  
  17.  
  18.  
  19. echo $activatecode;
  20.  
  21. ?>
  22.  
This is how salt look like.

Regards
Dheeraj Joshi
Aug 17 '09 #4
Dheeraj Joshi
1,123 Recognized Expert Top Contributor
MD5 is basically one way.

You can encrypt but can not decrypt..(I mean to say you can not get back the actual text from the encrypted text.)

Regards
Dheeraj Joshi
Aug 17 '09 #5
unauthorized
81 New Member
@dheerajjoshim
That's called "hashing". Encryption is always reversible e.g. encrypted text can be decrypted if you have the right key(s).

Ontopic, I would avoid md5() which is very outdated and easy to crack if I were you. If you want secure passwords, the best way would be to use some very resilient hashing algorithm (RipeMD is a great choice) with 6+ character salt. Encryption is slightly more problematic since the attacker only has to break the encryption key to access the data which means you will have to devise some method to protect the encryption keys (which is often done through hashing a password...). It's not worth all this hassle only to allow users to recover their password IMO.
Aug 17 '09 #6
Dheeraj Joshi
1,123 Recognized Expert Top Contributor
Unauthorized is right...

MD5 is outdated...

Go for something else.

Regards
Dheeraj Joshi
Aug 17 '09 #7
gopan
41 New Member
you can use base64_encode() and base64_decode() for encrypting and later decrypting the string...

Expand|Select|Wrap|Line Numbers
  1. <?php
  2. $str = 'This is a top secret...';
  3. $enc = base64_encode($str);
  4. $dec = base64_decode($enc);
  5.  
  6. echo "Encoded String";
  7. echo $enc;
  8. echo "Decoded String";
  9. echo $dec;
  10. ?>
  11.  
but its only 64 bit and not secure enough...

you may use hashing algorithms like MD5 and SHA1 to make a hash of your password and store it in the db..
later when the user enters the password... you just make the hash of the entered password and compare it with the hashed value from db with a strcmp()

Hope this will help you....
Aug 17 '09 #8
bbosh
4 New Member
base64_*() are not encryption algorithms; they are encoding algorithms. They convert from one form to another (like converting binary and decimal). By "64 bits" you mean "64 characters" and "not secure enough" should be "not secure at all".

You should take a look at mcrypt: http://uk.php.net/manual/en/function.mcrypt-encrypt.php

I'm not entirely sure, but I think MD5 is a fairly secure algorithm; SHA-1 is securer, I think. I wouldn't judge its strength by its age. Although it may be susceptible to brute force attacks, simple rate limiting on a production site can eliminate this risk.

As for salts, this is probably easier:

Expand|Select|Wrap|Line Numbers
  1. $salt = md5(uniqid(mt_rand(), true), true);
  2. $hashed_pass = md5 ( $pass . $salt, true);
  3.  
-Brendon.
Aug 19 '09 #9
dlite922
1,584 Recognized Expert Top Contributor
I cracked md5.

I have the code at home if you don't believe me.

It cracked a 4 letter password in half an hour. In a couple of days I could probably 5 or 6 letters.

I'd go with SHA-1 as a bare minimum with a good salt.



Dan
Aug 19 '09 #10

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