Скачать или смотреть Understanding Ed25519 Key Parsing and Verification in Java JDK 15

Learn how to parse a public key from a byte array and verify signatures using `Ed25519` in `Java JDK 15`. Detailed guide with code examples, common pitfalls, and troubleshooting tips.
---
This video is based on the question https://stackoverflow.com/q/65780235/ asked by the user 'Programmer' ( https://stackoverflow.com/u/6541172/ ) and on the answer https://stackoverflow.com/a/65818723/ provided by the user 'Programmer' ( https://stackoverflow.com/u/6541172/ ) 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: Ed25519 in JDK 15, Parse public key from byte array and verify

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.
---
A Comprehensive Guide to Parsing and Verifying Ed25519 Public Keys in Java JDK 15

The Ed25519 algorithm is gaining popularity for its security and performance in digital signatures. However, if you're working with it in Java JDK 15, you might encounter challenges -- especially when it comes to parsing public keys from byte arrays and verifying signatures.

In this guide, we will delve into the process of parsing and verifying Ed25519 keys, addressing common pitfalls, like those encountered while dealing with byte arrays. This guide aims to clarify these concepts for developers looking to implement Ed25519 in their applications effectively.

Overview of the Problem

When working with Ed25519 in Java, you may receive a public key in the form of a byte array, which is often sent by devices like iDevices. The challenge arises because the encoding of these keys can be complex, especially when converting between little-endian and big-endian formats to suit the Java framework requirements.

Here's a summary of common queries around this issue:

How to correctly parse the public key from a byte array?

What might cause the verification of the signature to fail?

Understanding Ed25519 Public Key Parsing

According to the Ed25519 specifications, the public key is derived from a point on an elliptic curve, which has a specific encoding. Here's how to parse it correctly:

Key Parsing Steps

Extract the Y-Coordinate:

Grab the last byte of the public key to determine the y-coordinate and whether the x-coordinate is odd.

The last byte should be manipulated to set the most significant bit to zero (to comply with the encoding standard).

Reverse the Byte Array:

The y-coordinate is encoded in little-endian format. To convert it to a BigInteger, reverse the array to achieve a big-endian format.

Create the Ed25519 Public Key:

Utilize the Java Cryptography Architecture (JCA) to build the public key using the parsed values.

Example Code Snippet

Here is an example code snippet that demonstrates the above steps:

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

Troubleshooting Verification Failures

If you've followed the parsing steps correctly but your verification fails, there are a few areas you can investigate:

Double Reversal Issue:

Ensure you're not reversing the array too many times. This was a common mistake encountered; reversing it once is usually sufficient for proper encoding.

Data Integrity:

Confirm that your device's public key and signature are intact and haven't been altered in transit.

Correct Hashing:

Ensure that the data you are verifying (e.g., deviceInfo) is concatenated correctly before signing.

Conclusion

Working with Ed25519 in Java JDK 15 can be complex, but understanding the processes of parsing byte arrays and verifying signatures simplifies the task significantly. Following the steps outlined in this guide should equip you to avoid common pitfalls and successfully implement Ed25519 in your projects.

If you have further questions or need assistance, feel free to drop a comment or reach out. Happy coding!