Generate 32 Byte Key Php

Posted : admin On 17.12.2020

Here is a high-level description of how this library works. Any discrepancybetween this documentation and the actual implementation will be considereda security bug.

Let's start with the following definitions:

PHP OpenSSL functions opensslencrypt and openssldecrypt seem to use PKCS5/7 style padding for all symmetric ciphers. Upon this, you can't use them to encrypt using null byte padding or to decrypt null byte padded data.

  • Generates a string of pseudo-random bytes, with the number of bytes determined by the length parameter. It also indicates if a cryptographically strong algorithm was used to produce the pseudo-random bytes, and does this via the optional cryptostrong parameter.
  • Random String Generator. This form allows you to generate random text strings. The randomness comes from atmospheric noise, which for many purposes is better than the pseudo-random number algorithms typically used in computer programs.
  • HKDF-SHA256(k, n, info, s) is the key derivation function specified inRFC 5869 (using the SHA256 hash function). The parameters are:
    • k: The initial keying material.
    • n: The number of output bytes.
    • info: The info string.
    • s: The salt.
  • AES-256-CTR(m, k, iv) is AES-256 encryption in CTR mode. The parametersare:
    • m: An arbitrary-length (possibly zero-length) message.
    • k: A 32-byte key.
    • iv: A 16-byte initialization vector (nonce).
  • PBKDF2-SHA256(p, s, i, n) is the password-based key derivationfunction defined in RFC 2898 (using the SHA256 hash function). The parametersare:
    • p: The password string.
    • s: The salt string.
    • i: The iteration count.
    • n: The output length in bytes.
  • VERSION is the string 'xDExF5x02x00'.
  • AUTHINFO is the string 'DefusePHP V2 KeyForAuthentication'.
  • ENCRINFO is the string 'DefusePHP V2 KeyForEncryption'.

To encrypt a message m using a 32-byte key k, the following steps are taken:

  1. Generate a random 32-byte string salt.
  2. Derive the 32-byte authentication key akey = HKDF-SHA256(k, 32, AUTHINFO, salt).
  3. Derive the 32-byte encryption key ekey = HKDF-SHA256(k, 32, ENCRINFO, salt).
  4. Generate a random 16-byte initialization vector iv.
  5. Compute c = AES-256-CTR(m, ekey, iv).
  6. Combine ctxt = VERSION saltivc.
  7. Compute h = HMAC-SHA256(ctxt, akey).
  8. Output ctxth.

Decryption is roughly the reverse process (see the code for details, since thesecurity of the decryption routine is highly implementation-dependent).

For encryption using a password p, steps 1-3 above are replaced by:

Php Byte Array

  1. Generate a random 32-byte string salt.
  2. Compute k = PBKDF2-SHA256(SHA256(p), salt, 100000, 32).
  3. Derive the 32-byte authentication key akey = HKDF-SHA256(k, 32, AUTHINFO, salt)
  4. Derive the 32-byte encryption key ekey = HKDF-SHA256(k, 32, ENCRINFO, salt)

Php Generate 32 Byte Key

The remainder of the process is the same. Notice the reuse of the same saltfor PBKDF2-SHA256 and HKDF-SHA256. The prehashing of the password in step 2 isdone to prevent a DoS attack using longpasswords.

Rails no master.key generated. For KeyProtectedByPassword, the serialized key is encrypted according to thepassword encryption defined above. However, the actual password used forencryption is the SHA256 hash of the password the user provided. This is done inorder to provide domain separation between the message encryption in the user'sapplication and the internal key encryption done by this library. It fixesa key replacement chosen-protocolattack.

PHP provides the popular md5() hash function out of the box, which returns 32 a hex character string. It’s a great way to generate a fingerprint for any arbitrary length string. But what if you need to generate an integer fingerprint out of a URL?

Challenge

We faced that challenge in RatingWidget when we had to bind our rating widgets to a unique Int64 IDs based on the website’s page it’s being loaded from. Theoretically we could just store the URLs and query the URL column, but URLs can be very long and creating an index for text column with unknown length is very inefficient.

So if you are working on any kind of dynamic widget development that should load different data based on the URL it’s loaded from, this post will save you tonnes of time.

To simplify the problem, let’s divide it into two sub-challenges:

  1. URL Canonization
  2. String to unique Int64 conversion
Byte

URL Canonization

Php Byte Data

In our case, we wanted to assign a unique Int64 for a page, not for a URL. For instance, http://domain.com?x=1&y=2 and http://domain.com?y=2&x=1 are different URLs but in fact both of them will load the exact same page. Therefore, we wanted to assign them an identical Int64 ID. Thus, by canonizing the URLs before mapping them to Int64, we can convert the URLs to uniform representation.

Basically what this code does is reorder the query string parameters by lexicographical order, and slightly tweak the URL encoding based on RFC 3986 URI syntax standard, to compensate for the different browsers + server URL encoding inconsistency.

Notes:

  1. In our case canonizeUrl, the canonization function, gets rid of the protocol. So https://domain.com and http://domain.com are both canonized to domain.com because we wanted to show the same rating widget on HTTP and HTTPS equivalent pages.
  2. As you can notice, we also ignore everything the after hashmark fragment. Therefore, if you would like to generate unique IDs for SPA (Single Page Application) different states like http://my-spa.com/#state1 and http://my-spa.com/#state2, the URL canonization function has to be modified to support that.

Generate 32 Byte Key Php Software

Converting String to unique Int64 ID for MySql BIGINT Indexed Column

After fooling around with various bit conversion functions like bindec(), decbin(), base_convert(). We have found out that 64 bit integers and PHP are not playing well. None of the mentioned functions consistently supports 64 bit. After digging around on Google, we were lead to a post about 32 bit limitations in PHP which included the suggestion to use GMP, a really cool library for multiple precision integers. Using this library, we managed to create this one line hash function that generates a 64 bit integer out of arbitrary length string.

Post factum, we could have implemented the CRC64 algorithm which generates a string checksum and should perform faster than MD5. But the advantage of the technique we’ve used over CRC is that we’ve created a one-way-hash function, so we can reuse it for various cryptography purposes in the code.

To find out more about GMP, see here.

Grand Finale

Combining the URL canonization with the String to Int64 mapping, the final solution looks like this:

Collision and Performance Test of get64BitHash

Universal key generator 2017 download. Platform: Intel i3, Windows 7 64 bit, PHP 5.3
Iterations: 10,000,000 Times generated get64BitHash
Elapsed Time: 460 millisecond for every 100,000 generations
Collision: Not found

Generate 32 Byte Key Php Login

Summary

Php Array Key

I hope this straightforward solution will save you time on your next project. If you have comments or any additional use-cases where this technique can be applied, please feel free to comment below.