Digital signatures use asymmetric encryption to sign executable files and verify their authenticity. A code signing certificate creates these signatures, which developers use to protect their software.
The process uses a private key to create the signature and a public key to verify it. Microsoft Authenticode, Java JAR signing, and Apple’s code signing system are common examples. These signatures help users confirm that software comes from trusted sources and hasn’t been tampered with.
Operating systems like Windows, macOS, and Linux check these signatures before running executables, showing warnings if signatures are invalid or missing.
What Is Asymmetric Encryption?
Asymmetric encryption (also referred to as public key encryption) is a form of cryptography that employs two keys: a public key and a private key.
These keys are connected but perform distinct roles:
- Public Key: Exposed to the public and is utilized for encrypting data or signing.
- Private Key: This is secret and is utilized for decrypting data or signing.
How Does Asymmetric Encryption Digitally Sign an Executable?
Digital signatures are the real time application of asymmetric encryption.
Following is the procedure that is followed while signing an executable file:
1. Executable File Hashing
- The first operation is to compute the hash value of the executable file. A hash is a sequence of characters of a certain length produced by a hash function (such as SHA-256). This hash is a representation of the file’s content.
- Any alteration in the file will result in a different hash value, thus giving a proof of the integrity of the file.
2. Hashing the Hash using the Private Key
- The hash is then encrypted using the private key of the developer of the software or the organization. This encrypted hash is a digital signature.
- Only the owner can sign something, thus the private key provides proof of authenticity.
3. The Signature is appended to the Executable
- The digital signature of the file is appended to the executable file and may also be accompanied by the public key of the developer. This certificate contains the public key and other information including the certificate authority that certified the developer.
4. The Signature Verification Process
When a user downloads the executable, the user’s system checks the signature by:
- Decrypting the signature using the public key to get the hash.
- Calculating the hash value of the downloaded file.
- The comparison of the hashes. If the two hashes match, then the file is genuine and has not been altered.
What Uses Asymmetric Encryption for Digital Signatures?
Several technologies and systems use asymmetric encryption to digitally sign executables:
1. Code Signing Certificates
- The code signing certificates are gotten from Certificate Authorities (CAs) and the developers use them to sign the executables, scripts and software updates.
- Other CAs include DigiCert, Sectigo and
2. Operating Systems
Digital signatures are used by modern operating systems to validate the software they are installing.
- Windows: Uses Authenticode technology to sign and validate executables.
- macOS: For apps not gotten from the App Store, the developer must sign the app with a Developer ID.
- Linux: Signed software packages can be verified using GPG (GNU Privacy Guard).
3. Software Distribution Platforms
- Developers are required to sign their software before publishing it on platforms such as Microsoft Store, Apple App Store, and Google Play.
- This way, users can be sure of the software they are downloading.
4. Blockchain and Smart Contracts
- Asymmetric encryption is employed in signing transactions and smart contracts in the block chain systems to prove their source and sanity.
Why Is Digital Signing Important?
Digital signing offers crucial advantages:
1. Authenticity
- The user is able to check if the software is genuine and has been modified by a party other than the owner.
2. Integrity
- Should any alteration be made to the executable file after the signing, the signature will be voided, thus warning the user of the possible tampering.
3. Non-Repudiation
- The developer is unable to refute the fact that they signed the software since only they hold the private key.
4. Trust
- Signed software is less of a threat to users and operating systems, thus reducing the likelihood of malware infections to some extent.
What are the Best Practices for Digitally Signing Executables?
Ensuring Effective Use of Asymmetric Encryption for Digital Signing
- A Reputable Certificate Authority (CA) should be used: Get your code signing certificate from a trusted CA for general acceptance and credibility.
- Your Private Key Protection: The private key should be stored securely and if possible, in a hardware security module (HSM) or a secure key vault.
- Every Software Update Should Be Signed: Guarantee A signed initial release, and all updates and
- Your Signatures Should Be Timestamped: Including the timestamp makes the signature valid even after the certificate has expired.
- Regularly Update Certificates: This is done to ensure that code signing certificates are not expired in order to avoid any interruption.
Final Thoughts
Asymmetric encryption is the basis of digital signatures, which are used for authenticating software and confirming its goodness. This process is used by code signing certificates, operating systems and software distribution platforms to protect the user from bad software. In this article, you will learn about how asymmetric encryption works and what you should do to secure your application.
The use of best practices while developing the applications will help the developers in gaining the trust of their customers and in turning towards a secure digital world. Whether you are a software engineer, or a normal citizen, it is crucial to know about digital signatures in the contemporary world.
Priya Mervana
Verified Web Security Experts
Priya Mervana is working at SSLInsights.com as a web security expert with over 10 years of experience writing about encryption, SSL certificates, and online privacy. She aims to make complex security topics easily understandable for everyday internet users.
