How Can PHP Securely Encrypt, Decrypt, and Hash Data for Web Applications?

Implementing Encryption/Decryption and Hashing in PHP

Introduction

In web development, it's essential to protect sensitive user data by encrypting it before storing it in a database. PHP provides robust encryption and hashing capabilities to enhance data security.

Encryption

Symmetric Encryption:

To encrypt data symmetrically, PHP uses the OpenSSL extension. Consider using AES-256-CBC with a secure encryption key and an initialisation vector (IV) for randomness. Encrypt the data in chunks of 16 bytes and store both the encrypted data and IV in your database.

Authenticated Encryption:

For added security, append a signature to your encrypted data using a separate authentication key. This will allow you to verify the integrity of the data before decryption.

Decryption

Follow the same encryption algorithm with the same secret key and IV to decrypt the data securely. Optionally, authenticate the encrypted data again before decrypting it.

Hashing

Password Hashing:

Avoid storing user passwords in plaintext. Instead, hash them using a slow and secure algorithm like bcrypt. Bcrypt uses a salt to make brute-force attacks computationally expensive.

Verification:

To verify a password against its hashed equivalent, use the crypt() function or its PHP 5.5 equivalent, password_verify(). Utilize constant-time comparison to prevent timing attacks.

Example Implementation

Encryption:

Decryption:

Password Hashing:

Verification:

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