Introduction
In this article, we will discuss an issue encountered while signing a binary file using two different methods with OpenSSL, resulting in different signatures. We will explore the key concepts related to this topic, including digital signatures, hashing algorithms, and the differences between the two methods used.
Digital Signatures and Hashing Algorithms
A digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents. It uses a cryptographic algorithm to ensure that the contents of a message have not been altered during transmission. A hashing algorithm is a function that maps data of arbitrary size to a fixed size. It is used in digital signatures to ensure the integrity of the data being signed.
Method 1: Signing a Binary File with OpenSSL
The first method we used to sign a binary file with OpenSSL is as follows:
openssl dgst -sha256 -sign private.pem -out signature.bin binary\_file.bin
This command calculates the SHA-256 hash of the binary file and signs it using the private key in the private.pem file. The resulting signature is saved in the signature.bin file.
Method 2: Signing a Binary File with OpenSSL and PKCS7
The second method we used to sign a binary file with OpenSSL is as follows:
openssl smime -sign -in binary\_file.bin -signer cert.pem -inkey private.pem -outform DER -out signature.bin
This command calculates the SHA-256 hash of the binary file, signs it using the private key in the private.pem file, and wraps the signature in a PKCS7 container. The resulting signature is saved in the signature.bin file.
Differences between the Two Methods
The two methods produce different signatures for the same binary file. The first method produces a raw signature, while the second method produces a PKCS7-formatted signature. The PKCS7 format includes additional information, such as the certificate used to sign the file and the algorithm used to sign it. This additional information makes the PKCS7-formatted signature larger than the raw signature produced by the first method.
In this article, we have explored the issue of different results when signing a binary file using two different methods with OpenSSL. We have discussed the key concepts related to this topic, including digital signatures and hashing algorithms. We have also examined the differences between the two methods used and their respective outputs. By understanding these concepts and differences, we can ensure the integrity and authenticity of our digital messages and documents.