README.md

First-time generated IV then file-persisted use

The example goes through the following steps:

1. require all the necessary modules:

   • crypto, the test subject;
   • fs, read and write simple text files;
   • path, resolve file paths;
   • assert, test the result of the operations;

2. setup some utility objects and the cryptography-related functions, including a key that goes through SHA256 (AES-256 requires 256 bits of key (32 Bytes)); Note: Differently from example1, the encrypt function now appends the encrypted content after the IV buffer (which is not encrypted in any way).

3. if the encrypted file is missing, a generation function creates it with following rules:

   • a 16 bytes long IV is created using the crypto module's randomBytes function
   • the encrypted content is written to disk as a utf8 encoded hex string.
     HEX(*plain text* IV + *encrypted* content)

4. read synchronously the encrypted text file from disk and store it in memory (utf8 encoding);

5. from the read encrypted file extract the first 16 bytes since they are the IV used during the encryption process;

6. from the read encrypted file extract everything past the first 16 bytes as it is the actual encrypted content;

7. decrypt the encrypted content using the extracted IV and the provided secret (fixed);

8. simple test using Node's integrated assert function (match between plain text and decrypted content).

Warnings

There are in a few occasions unnecessary convertions from Buffer instances to string instances. They are there for convenience purposes (debug) since the crypto module's functions transform strings into buffers internally anyway.