Nov 09, 2017 Before you do anything further, seek to understand the difference between encryption and authentication, and why you probably want authenticated encryption rather than just encryption. To implement authenticated encryption, you want to Encrypt then MAC. The order of encryption and authentication is very important! I'm late to the party, but searching for the correct way to do it I came across this page it was one of the top Google search returns, so I will like to share my view on the problem, which I consider it to be up to date at the time of writing this post (beginning of 2017).
Php /. Simple PHP Encryption functions. Attempts to be as secure as possible given:. Key can be any string. No knowledge of encryption is required. Nov 15, 2015 Encrypt your message using Defuse Security's PHP symmetric-key encryption library Encrypt the ephemeral key with the given RSA public key (using a mode that actually isn't vulnerable to padding oracles) Base64-encode and concatenate both ciphertexts with a version tag prefix. Ask questions about frameworks, try your hand at php golf and strike gold or simply show off your latest work. Generating Random Passwords in PHP. Generating unbiased random passwords is a surprisingly non-trivial problem. Most naive solutions, such as taking the remainder of a random integer or shuffling a string, lead to biases in the passwords.
Hello! If you're reading this file, it's because you want to add encryption toone of your PHP projects. My job, as the person writing this documentation, isto help you make sure you're doing the right thing and then show you how to usethis library to do it. To help me help you, please read the documentationcarefully and deliberately.
A Word of Caution
Encryption is not magic dust you can sprinkle on a system to make it moresecure. The way encryption is integrated into a system's design needs to becarefully thought out. Sometimes, encryption is the wrong thing to use. Othertimes, encryption needs to be used in a very specific way in order for it towork as intended. Even if you are sure of what you are doing, we stronglyrecommend seeking advice from an expert.
The first step is to think about your application's threat model. Ask yourselfthe following questions. Who will want to attack my application, and what willthey get out of it? Are they trying to steal some information? Trying to alteror destroy some information? Or just trying to make the system go down so peoplecan't access it? Then ask yourself how encryption can help combat those threats.If you're going to add encryption to your application, you should have a veryclear idea of exactly which kinds of attacks it's helping to secure yourapplication against. Once you have your threat model, think about what kinds ofattacks it does not cover, and whether or not you should improve your threatmodel to include those attacks.
This isn't for storing user login passwords: The most common use ofcryptography in web applications is to protect the users' login passwords. Ifyou're trying to use this library to 'encrypt' your users' passwords, you're inthe wrong place. Passwords shouldn't be encrypted, they should be hashedwith a slow computation-heavy function that makes password guessing attacks moreexpensive. See How to Safely Store Your Users' Passwords in2016.
This isn't for encrypting network communication: Likewise, if you're tryingto encrypt messages sent between two parties over the Internet, you don't wantto be using this library. For that, set up a TLS connection between the twopoints, or, if it's a chat app, use the SignalProtocol.
What this library provides is symmetric encryption for 'data at rest.' Thismeans it is not suitable for use in building protocols where 'data is in motion'(i.e. moving over a network) except in limited set of cases.
Please note that encryption does not, and is not intended to, hide thelength of the data being encrypted. For example, it is not safe to encrypta field in which only a small number of different-length values are possible(e.g. Free microsoft office 2013 product key generator. 'male' or 'female') since it would be possible to tell what the plaintextis by looking at the length of the ciphertext. In order to do this safely, it isyour responsibility to, before encrypting, pad the data out to the length of thelongest string that will ever be encrypted. This way, all plaintexts are thesame length, and no information about the plaintext can be gleaned from thelength of the ciphertext.
Getting the Code
There are several different ways to obtain this library's code and to add it toyour project. Even if you've already cloned the code from GitHub, you shouldtake steps to verify the cryptographic signatures to make sure the code you gotwas not intercepted and modified by an attacker.
Please head over to the Installing andVerifying documentation to get the code, and thencome back here to continue the tutorial.
Using the Library
I'm going to assume you know what symmetric encryption is, and the differencebetween symmetric and asymmetric encryption. If you don't, I recommend takingDan Boneh's Cryptography I course onCoursera.
To give you a quick introduction to the library, I'm going to explain how itwould be used in two sterotypical scenarios. Hopefully, one of these sterotypesis close enough to what you want to do that you'll be able to figure out whatneeds to be different on your own.
Formal Documentation
While this tutorial should get you up and running fast, it's important tounderstand how this library behaves. Please make sure to read the formaldocumentation of all of the functions you're using, since there are someimportant security warnings there.
The following classes are available for you to use:
Scenario #1: Keep data secret from the database administrator
In this scenario, our threat model is as follows. Alice is a serveradministrator responsible for managing a trusted web server. Eve is a databaseadministrator responsible for managing a database server. Dave is a webdeveloper working on code that will eventually run on the trusted web server.
Let's say Alice and Dave trust each other, and Alice is going to host Dave'sapplication on her server. But both Alice and Dave don't trust Eve. They knowEve is a good database administrator, but she might have incentive to steal thedata from the database. They want to keep some of the web application's datasecret from Eve.
In order to do that, Alice will use the included
generate-defuse-key scriptwhich generates a random encryption key and prints it to standard output:
Alice will run this script once and save the output to a configuration file, sayin
/etc/daveapp-secret-key.txt and set the file permissions so that only theuser that the website PHP scripts run as can access it.
Dave will write his code to load the key from the configuration file:
Then, whenever Dave wants to save a secret value to the database, he will firstencrypt it:
Whenever Dave wants to get the value back from the database, he must decrypt itusing the same key:
Note that if anyone ever steals the key from Alice's server, they can decryptall of the ciphertexts that are stored in the database. As part of our threatmodel, we are assuming Alice's server administration skills and Dave's securecoding skills are good enough to stop Eve from being able to steal the key.Under those assumptions, this solution will prevent Eve from seeing data that'sstored in the database.
However, notice that our threat model says nothing about what could happen ifEve wants to modify the data. With this solution, Eve will not be able toalter any individual ciphertext (because each ciphertext has its owncryptographic integrity check), but Eve will be able to swap ciphertexts forone another, and revert ciphertexts to what they used to be at previous times.If we needed to defend against such attacks, we would have to re-design ourthreat model and come up with a different solution.
Scenario #2: Encrypting account data with the user's login password
This scenario is like Scenario 1, but subtly different. The threat model is asfollows. We have Alice, a server administrator, and Dave, the developer. Aliceand Dave trust each other, and Alice wants to host Dave's web application,including its database, on her server. Alice is worried about her server gettinghacked. The application will store the users' credit card numbers, and Alicewants to protect them in case the server gets hacked.
We can model the situation like this: after the server gets hacked, the attackerwill have read and write access to all data on it until the attack is detectedand Alice rebuilds the server. We'll call the time the attacker has access tothe server the exposure window. One idea to minimize loss is to encrypt theusers' credit card numbers using a key made from their login password. Then, aslong as the users all have strong passwords, and they are never logged in duringthe exposure window, their credit cards will be protected from the attacker.
To implement this, Dave will use the
KeyProtectedByPassword class. When a newuser account is created, Dave will save a new key to their account, one that'sprotected by their login password:
WARNING: Because of the way
KeyProtectedByPassword is implemented, knowingSHA256($password) is enough to decrypt a KeyProtectedByPassword . To besecure, your application MUST NOT EVER compute SHA256($password) and use orstore it for any reason. You must also make sure that other libraries yourapplication is using don't compute it either.
Php Defuse Crypto Generate Encryption Key Download
Then, when the user logs in, Dave's code will load the protected key from theuser's account record, unlock it to get a
Key object, and save the Key object somewhere safe (like temporary memory-backed session storage). Note thatwherever Dave's code saves the key, it must be destroyed once the user logs out,or else the attacker might be able to find users' keys even if they were neverlogged in during the attack.
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When a user adds their credit card number, Dave's code will get the key from thesession and use it to encrypt the credit card number:
When the application needs to use the credit card number, it will decrypt it:
With all caveats carefully heeded, this solution limits credit card numberexposure in the case where Alice's server gets hacked for a short amount oftime. Remember to think about the attacks that aren't included in our threatmodel. The attacker is still free to do all sorts of harmful things likemodifying the server's data which may go undetected if Alice doesn't have securebackups to compare against.
Getting Help
If you're having difficulty using the library, see if your problem is alreadysolved by an answer in the FAQ.
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encrypt-decrypt.php
Php Defuse Crypto Generate Encryption Key For Windows 7
example.php
commented Mar 9, 2019
Php Defuse Crypto Generate Encryption Key File
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