How to verify decryption failure?

To verify decryption failure, you can compare the decrypted file with the original file using the diff command. If the files differ, it indicates that the decryption was unsuccessful. Here’s how you can do it:

Attempt to decrypt the file with the wrong password:

openssl enc -aes-256-cbc -d -in secret.enc -out wrong.txt -pbkdf2

Use the diff command to compare the original file (secret.txt) with the decrypted file (wrong.txt):
```
diff secret.txt wrong.txt
```
If the diff command produces output, it means the files are different, confirming that the decryption failed. If there is no output, it indicates that the files are identical, which is unexpected in the case of a wrong password.

You can also check the contents of the decrypted file to see if it appears scrambled or nonsensical, which would further indicate a failure in decryption. Use the cat command to view the contents:

cat wrong.txt