Creating a random validation code for email confirmation when registering as a new user

I want to create a secure random code that the user must click on in an email to activate their account. I have read a few posts on google and as usual, everybody has a different opinion! It seems though that a decent one is random_bytes. Is this acceptable? Also, I don't know how to actually use it. I tried this but it has symbols as well which I don't think I can store in a database?

I did this:

$identifier = random_bytes(12);
echo (bin2hex($identifier));

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which generated : 2111d60a465f2f8c31ab7596

Is that sufficient or is there a more secure method?
Black SulfurAsked:
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Ray PaseurCommented:
One issue with random_bytes() is that it may generate character strings that are not binary-transport safe.  Email is sensitive about such things.  Almost any string will work for a token.  The important characteristics are (1) the token must be unique and (2) the token must not be easy to guess.

Here's a full explanation complete with working code you can copy and install.

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Black SulfurAuthor Commented:
Thanks, Ray. I see this article was written in 2010. Have you updated the code since then or is it still code from 2010?
Ray PaseurCommented:
It is still code from 2010, and it still works just fine.  You're smart to notice the date -- there are a lot of outdated examples scattered about the internet.  Here at E-E we try to update the articles as the technology advances.  There is an update trail, but I don't believe anybody except the authors and the editors can see it.  This one was last updated in 2015, IIRC.
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Black SulfurAuthor Commented:
Okay, great. 2015 sounds good. I just ask because with php 7 there are a lot of "better" ways to do things and more secure. So, I would rather try learn using the latest methods.

But like you said, the article was updated in 2015 so that is great, I will check it out. Thanks so much!
Ray PaseurCommented:
Agreed, it's always best to use the latest methods.  But as a friend of mine has said, "Good programmers recognize great programming.  Great programmers recognize good-enough programming!"

Black SulfurAuthor Commented:
Just to confirm, is it okay to use MD5 for this? Please note that I am still new to this and there is so much information out there it makes my head spin sometimes as everybody has their own opinion. Anyway, from what I understand, MD5 is not good enough anymore for storing passwords, so I use the password_hash and BCRYPT.

BUT, this isn't for storing a password in the database so I just wanted to confirm that MD5 is still okay as per your article.
Dave BaldwinFixer of ProblemsCommented:
MD5 is still widely used for hashing passwords because it is 'good enough' in most situations.  The 'goodness' of encryptions depends as much on the value of the information as the method of encryption.  If there is no financial value to breaking the encryption, then any method that makes it difficult to guess is 'good enough'.  If there is credit card data or other financial info that needs to be protected, then other people have a lot more interest in 'breaking in' to steal the info.
Ray PaseurCommented:
...this isn't for storing a password in the database so I just wanted to confirm that MD5 is still okay...
Yep, it's still OK in this context and many other contexts, too.  

For a little more perspective on md5() and other encoding / encryption techniques, see the discussion at the end of this article: See An Afterword: About Storing Passwords
Julian HansenCommented:
My preference is to use GUID's which can be generated in code or if you are using a MySQL server with a simple query. GUID's are in common use for this sort of application - the string is guaranteed to be unique and is non guessable so it satisfies all the requirements you are looking for.

Assumes MySQLi
$result=$mysqli->query("SELECT UUID()");
$row = $result->fetch_row();
$uuid = $row[0];

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