Encrypt a File with x509 Certificate Using cfssl and openssl

Описание: Learn how to effectively use an `x509` certificate for encryption and decryption with `cfssl` and `openssl`. This guide helps troubleshoot common issues in the process.
---
This video is based on the question https://stackoverflow.com/q/73075991/ asked by the user 'Manel R. Doménech' ( https://stackoverflow.com/u/15297860/ ) and on the answer https://stackoverflow.com/a/73077332/ provided by the user 'dave_thompson_085' ( https://stackoverflow.com/u/2868801/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Encrypt a file with a x509 certificate with cfssl and openssl

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Encrypt a File with x509 Certificate Using cfssl and openssl

In this guide, we address a common challenge faced by developers and IT professionals when they need to secure sensitive data. The question at hand is how to encrypt files using an x509 certificate, specifically when the tools in question are cfssl and openssl.

Many users find themselves able to sign documents easily but struggle with the encryption process. In this guide, we'll break down the solution and provide clarity on the use of x509 certificates for encryption.

Understanding the Problem

You have generated an x509 certificate using cfssl, which includes a certificate file (server.pem) and its corresponding private key (server-key.pem). After successfully verifying the certificate and signing a file, the next step is encryption. However, many face errors when trying to encrypt files.

Common Errors Encountered

Recipient Certificate Not Found

[[See Video to Reveal this Text or Code Snippet]]

Error: could not read recipient certificate file from server-key.pem.

Unsupported Key Type

[[See Video to Reveal this Text or Code Snippet]]

Error: encryption not supported for this key type.

Misunderstanding PKCS-12 Format

[[See Video to Reveal this Text or Code Snippet]]

Error: encryption not supported for this key type.

These errors highlight that the encryption process is more nuanced than simply using the existing files.

Steps to Solve the Problem

To successfully encrypt a file using your x509 certificate, follow these steps:

1. Verify the Public Key Algorithm

Before you start encrypting, ensure that the public key algorithm in your certificate is suitable for encryption. Run the following command:

[[See Video to Reveal this Text or Code Snippet]]

Check the line labeled Public Key Algorithm:

If you see dsaEncryption or rsassaPss, those algorithms do not support encryption.

If it says id-ecPublicKey, the smime command cannot be used, but cms can be utilized instead.

2. Understanding Encryption vs Decryption Keys

To encrypt, you only need the public certificate. However, for decrypting, both the private key and the certificate are necessary. This means that attempts to concatenate files (like PEM files) to create a PKCS12 file will be misleading and could lead to further errors.

3. Correctly Encrypting a File

If your certificate is compatible, you can use cms for encryption as follows:

[[See Video to Reveal this Text or Code Snippet]]

This command encrypts the file secret.txt using your x509 certificate.

Conclusion

Successfully using cfssl and openssl for encryption with x509 certificates requires verification of the certificate's public key algorithm and understanding the separation of encryption and decryption keys.

By following these guidelines, you can effectively encrypt sensitive information without running into the common pitfalls most users encounter. If you continue to face issues, check if your key algorithm supports encryption or consider using the correct command format.

Remember, encryption is a crucial aspect of securing data in transit and at rest, and smooth implementation can save you considerable time and hassle down the road!