How to Migrate from Mcrypt to OpenSSL without Significant Code Changes?

Migrating from Mcrypt to OpenSSL without Extensive Recoding

Background:

Your PHP application currently utilizes Mcrypt for data encryption with a Blowfish cipher and ECB mode. However, you face the challenge of migrating to OpenSSL for encryption.

Key Differences:

• OpenSSL uses PKCS#7 padding while Mcrypt uses PKCS#5.
• OpenSSL does not require an Initialization Vector (IV) in ECB mode, unlike Mcrypt.

Solution:

To seamlessly migrate without significant recoding, follow these steps:

1. Recreate Encrypted Data: Manually pad the data with PKCS#7 before encrypting it with Mcrypt. Example code is provided below:

   $key = "anotherpassword1";
   $str = "does it work 12";
   $enc = mcrypt_encrypt(MCRYPT_BLOWFISH, $key, $str."", MCRYPT_MODE_ECB);

2. Use OpenSSL for Decryption: After recreating the encrypted data, use OpenSSL to decrypt it using the correct cipher and mode:

   $key = "anotherpassword1";
   $enc = "0e93dce9a6a88e343fe5f90d1307684c";
   $dec = openssl_decrypt($enc, 'bf-ecb', $key, true);
   echo $dec;

Note: You mentioned that different IV lengths were needed for Mcrypt (56) and OpenSSL (0). However, ECB mode does not utilize IVs.

By following these steps, you can migrate from Mcrypt to OpenSSL without the need for extensive code modifications, ensuring compatibility with your existing encrypted data.

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