Openssl Aes 256 Key Generation
Introduction
Openssl Aes 256 Cbc
For AES-128, the key can be recovered with a computational complexity of 2 126.1 using the biclique attack. For biclique attacks on AES-192 and AES-256, the computational complexities of 2 189.7 and 2 254.4 respectively apply. Related-key attacks can break AES-192 and AES-256 with complexities 2 176 and 2 99.5 in both time and data, respectively. While Encrypting a File with a Password from the Command Line using OpenSSL is very useful in its own right, the real power of the OpenSSL library is its ability to support the use of public key cryptograph for encrypting or validating data in an unattended manner (where the password is not required to encrypt) is done with public keys.
Laravel's encrypter uses OpenSSL to provide AES-256 and AES-128 encryption. You are strongly encouraged to use Laravel's built-in encryption facilities and not attempt to roll your own 'home grown' encryption algorithms. All of Laravel's encrypted values are signed using a message authentication code (MAC) so that their underlying value can not be modified once encrypted.
Configuration
Openssl Aes 256 Key Generation Manual
Before using Laravel's encrypter, you must set a key option in your config/app.php configuration file. You should use the php artisan key:generate command to generate this key since this Artisan command will use PHP's secure random bytes generator to build your key. If this value is not properly set, all values encrypted by Laravel will be insecure.
Using The Encrypter
Encrypting A Value
You may encrypt a value using the encrypt helper. All encrypted values are encrypted using OpenSSL and the AES-256-CBC cipher. Furthermore, all encrypted values are signed with a message authentication code (MAC) to detect any modifications to the encrypted string:
Encrypting Without Serialization
Encrypted values are passed through serialize during encryption, which allows for encryption of objects and arrays. Thus, non-PHP clients receiving encrypted values will need to unserialize the data. If you would like to encrypt and decrypt values without serialization, you may use the encryptString and decryptString methods of the Crypt facade:
Decrypting A Value
Aes Key Gen
You may decrypt values using the decrypt helper. If the value can not be properly decrypted, such as when the MAC is invalid, an IlluminateContractsEncryptionDecryptException will be thrown:
Creating and managing keys is an important part of the cryptographic process. Symmetric algorithms require the creation of a key and an initialization vector (IV). The key must be kept secret from anyone who should not decrypt your data. The IV does not have to be secret, but should be changed for each session. Asymmetric algorithms require the creation of a public key and a private key. The public key can be made public to anyone, while the private key must known only by the party who will decrypt the data encrypted with the public key. This section describes how to generate and manage keys for both symmetric and asymmetric algorithms.
Symmetric Keys
The symmetric encryption classes supplied by the .NET Framework require a key and a new initialization vector (IV) to encrypt and decrypt data. Whenever you create a new instance of one of the managed symmetric cryptographic classes using the parameterless constructor, a new key and IV are automatically created. Anyone that you allow to decrypt your data must possess the same key and IV and use the same algorithm. Generally, a new key and IV should be created for every session, and neither the key nor IV should be stored for use in a later session.
To communicate a symmetric key and IV to a remote party, you would usually encrypt the symmetric key by using asymmetric encryption. Sending the key across an insecure network without encrypting it is unsafe, because anyone who intercepts the key and IV can then decrypt your data. For more information about exchanging data by using encryption, see Creating a Cryptographic Scheme.
The following example shows the creation of a new instance of the TripleDESCryptoServiceProvider class that implements the TripleDES algorithm.
When the previous code is executed, a new key and IV are generated and placed in the Key and IV properties, respectively.
Sometimes you might need to generate multiple keys. In this situation, you can create a new instance of a class that implements a symmetric algorithm and then create a new key and IV by calling the GenerateKey and GenerateIV methods. The following code example illustrates how to create new keys and IVs after a new instance of the symmetric cryptographic class has been made.
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When the previous code is executed, a key and IV are generated when the new instance of TripleDESCryptoServiceProvider is made. Another key and IV are created when the GenerateKey and GenerateIV methods are called.
Asymmetric Keys
The .NET Framework provides the RSACryptoServiceProvider and DSACryptoServiceProvider classes for asymmetric encryption. These classes create a public/private key pair when you use the parameterless constructor to create a new instance. Asymmetric keys can be either stored for use in multiple sessions or generated for one session only. While the public key can be made generally available, the private key should be closely guarded.
A public/private key pair is generated whenever a new instance of an asymmetric algorithm class is created. After a new instance of the class is created, the key information can be extracted using one of two methods:
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The ToXmlString method, which returns an XML representation of the key information.
The ExportParameters method, which returns an RSAParameters structure that holds the key information.
Both methods accept a Boolean value that indicates whether to return only the public key information or to return both the public-key and the private-key information. An RSACryptoServiceProvider class can be initialized to the value of an RSAParameters structure by using the ImportParameters method.
Asymmetric private keys should never be stored verbatim or in plain text on the local computer. If you need to store a private key, you should use a key container. For more on how to store a private key in a key container, see How to: Store Asymmetric Keys in a Key Container.
The following code example creates a new instance of the RSACryptoServiceProvider class, creating a public/private key pair, and saves the public key information to an RSAParameters structure.