Obtaining uncompacted public keys in compacted forms

Ethereum’s public keys are typically stored as compact bytes strings. This makes it difficult to decominate and easily recover for use in various applications, such as sending transactions or interacting with intelligent contracts. However, understanding the decompression process of these bytes sequences can help you work more efficiently with Ethereum data.

The BitCoralk Forum Response

A question similar to this was asked in the BitcoRontalk Forum: [https: //bitcoinalk.org/index.php? …] (https: //bitcoinalk.org/index.php? …). The answer suggests that you can use OpenSSL to decompress the compacted public key. Here is an example of how to do so in Python:

`Python

Import X509 Cryptography

Import base64

Loading the compacted public key of memory

compressed_public_key = b ‘\ x8c \ x05 \ x15 \ x00 \ x01 \ x00 \ x03 \ x04 \ x1e \ x07 \ x08 \ x10 \ x12 \ x12 \ x12 \ x12 \ x12 \ x12 3 \ x14 \ x15 \ x16 \ x17 ‘

Create a certificate object x.509 from the compacted public key

public_key = x509.load_pem_x509_certificate (compressed_public_key)

Convert the certificate to a rope coded by Pem

Pem_String = public_key.public_bytes (

coding = base64,

format = x509.der_cert_raw

) .Decode (“UTF-8”)

Print (Pem_String)

`

Explanation

• We started by loading the compacted public key using x509.load_pem_x509_certificate (). This function obtains the sequence of compacted public key bytes as input.

• Then we created an object of certificate X.509 of the loaded public key using x509.load_pem_x509_certificate ().

• To convert the certificate into a sequence encoded by PEM, we use public_key.public_bytes (coding = base64, format = x509.der_cert_raw). This function takes the certificate and returns a sequence of bytes that contains the binary data from the public key.

• Finally, we print the uncontempted public key in hexadecimal format.

Using OpenSSL to decompress the public keys

To decompress the compacted public key using OpenSSL, you can use the OpenSSL tool. Here is an example:

`Bash

$ Openssl x509 -d -in -Out uncompressed_public_key.pem

`

Replace by the real bytes sequence of the compacted public key.

Observation

This method assumes that the compacted public key is in DER format (distinguished coding rules), which is the standard for X.509 certificates. If your public key is stored in a different format, you may need to use a different method to decompress it.

Understanding how to decompress compacted public keys using OpenSSL and Python, you can make your work with Ethereum data more efficient and convenient.