Best way to encode passwords in PHP

问题:

I currently use,
base64_encode() to encode a user's password, this works well because it allows me to simply use base64decode() to decode the password to a word and send to there email if they lose there password.

I have been reading up on password though and a lot of people seem to say that you should use sha1() to encode a password. I am all for improving my system's security but if I convert to use shal() then I will not be able to send a user there lost password.

What do YOU use? Can you give me some advice? And is there a way to decod to a readable password to email a user?

As I typed this question I just remebered that some forums do not send you a password when requested but instead send a special link to re-set your password, I am guessing that this is because they are unable to decode your password maybe?

//what I use now
$password_encoded = base64_encode($password);

//what I am considering using
$password_encoded = sha1($password);

回答1:

Please, please for the sake of your users do not store their passwords in any reversible format! It doesn't matter if it's Base64 encoded or triple-DES 168-bit encryption - if it is reversible, it is exactly as secure as if you didn't encode it at all.

No website that has any interest in protecting itself or its users (or has a lick of sense) will send a user their password via e-mail. The only thing we can do that's even remotely close to secure is to send users an email with a unique, one-time-use link that lets them set a new password.

• Store a hash (bcrypt or PBKDF2) of the password which has been salted
• Throw away the original password as soon as you've hashed it. Excise it from memory.
• Always require the user to create their own new password over an SSL channel

Trying to get by with anything else is honestly just negligence. Let's use a very common scenario used in security discussions:

User Frederic's email is compromised. This could be from leaving his computer unlocked or using a weak password. Regardless, an unauthorized person has access to his messages. Ideally, this would mean nothing more than some embarrassing love letters read by a stranger. Unfortunately, the unauthorized person discovers a forum will email Frederic's password in plain-text. Like most users, Frederic uses the same password for everything, including his online banking. His username is listed in an email from his bank. Now the situation is very unfortunate.

Users are placing trust in you when they create a credentials-based relationship with you. Part of that trust is that you will keep those credentials as a secure secret between you and them.

Related

A lot of the surrounding issues and ideas have been answered very well on SO:

• Difference between Hashing a Password and Encrypting it
• Why is challenge-response approach a poor solution for forgotten passwords?
• Non-random salt for password hashes

回答2:

As an administrator, you never actually need to recall the password of a user. You simply need to know if a string they've once submitted, is identical to another.

If a user forgets their password, they don't need to be told their old password, you can simply have them provide a new one.

Since you don't need to know the actual passwords, using a crytographic hash of the words would seem like a safe way to store them. However, large tables of pre-computed strings have been made to easily do a reverse-lookup of the hash back it's original string. These are called rainbow tables.

To avoid easy lookup of pre-computed string, you should salt your passwords before hashing them. The salt can be their username prepended, or their user ID postfixed, whatever extra information you have on the user that is permanent that you can easily add to the password during authentication.

回答3:

You should let a user RESET a password but never RETRIEVE their password. That is why you would want to use a one-way hash (SHA2) instead of a form of encryption that lets you decode it.

Imagine if you left your email open. I could simply request to retrieve your password for some website, delete the email, and you would never know. On the other hand, if you required me to reset the password instead, the account password would change and the owner would obviously realize that something is wrong. (This is a dumb scenario but the concept is what's important)

Hashes can be "reversed" by trying all possible combinations of words (or using rainbow tables) until a matching hash is produced. One way to avoid this is to append/prepend the provided password with a salt to make it a very long and unpredictable string. The salt should be a unique string of data unique to the individual's account.

In PHP there is no SHA2 functon. SHA-2 is a family of hash algorithms, (SHA-256, SHA-384, SHA-512, etc...)

hash('sha256', 'The quick brown fox jumped over the lazy dog.');

回答4:

An absolute must-read on this topic is Jeff's own You're Probably Storing Passwords Incorrectly. Here's the executive summary:

1. Do not invent your own "clever" password storage scheme.
2. Never store passwords as plaintext.
3. Add a long, unique random salt to each password you store.
4. Use a cryptographically secure hash.

回答5:

Base64Encode offer no security, because anybody can reverse it easily.

If you absolutely need to reverse the password, a good way is to use a secret question, and to use the answer as an encryption key. Once the password is encrypted, you throw the answer away (you do not store it). You also use the standard sha1 encryption for the time when you need to verify that he enter the right password. If the user want its password, he enter the answer to its secret question, and you use that to restore the password and send it back to him.

It's not as secure as hash based encryption only, but if you need to send back the password it's a good compromise.

You may want to look at the mcrypt library for php http://ca3.php.net/mcrypt

回答6:

I always delete my account only any sites that emails me my password. I put too much effort and time into memorizing long random passwords to have it sent to me in plain text.

Use sha1() or higher non-reversible hash to identify the password. When authenticating a user password, retrieve the hash, and compare it with the hash of the password supplied during authentication. If they match, then the user is authentic within reasonable standards.

$user = "joe";
$password = 'password';

$saved_hash = DB::Query("select hash from users where username = ".quote($user)." LIMIT 1");

if (sha256($password) == $saved_hash) User::authenticated();

Never, ever send passwords in email. Send a unique, non-predictable, generated key, such as in PHP:

$key = sha256(time().rand().$secret_seed);

Send this key to the client, for one time use, to set a new password.

回答7:

You will want to use a hash(preferably sha1) with "salt"

回答8:

You can do the hashing on the server when authenticating in one quick query:

SELECT * FROM user WHERE password = MD5(CONCAT(?, salt));