What is Token Signing in Code Signing Certificate?

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What is Token Signing in Code Signing

To prevent unauthorized access to federated resources, federation servers will enforce the use of token-signing certificates, effectively thwarting cybercriminals from tampering with or forging security tokens. The most crucial validation technique for any federated collaboration is the private/public key pairing utilized with token-signing certificates. These encryption keys verify that a security token was generated by an authorized/legitimate partner federation server and that it was not altered in transmission.

What is Token Signing?

Token signing is a procedure that requires getting a private signing key and using it to verify the identity of a single person or group of people who use tokens to access a system or service. To make sure that the digital signature on a code file is authorized and approved by a trustworthy certificate authority, this approach is frequently used in Code Signing Certificates.

Token-signing certificates are needed by federation servers in Active Directory Federation Services (AD FS) to stop attackers from modifying or forging security tokens to obtain unauthorized access to federated resources. Every token-signing certificate has public and private cryptographic keys used to digitally sign a security token (using the private key). The authenticity of the encrypted security token is later verified (using the public key) by a partner federation server after receiving these keys.

In this regard, FIPS 140-2 tokens can be used for token signing, as they contain the required cryptographic modules for handling digital signatures. Since the signed documents are handled in a licensed and secure environment, this guarantees that they are safe and tamper-proof. As they cooperate in providing a safe digital signature method for sensitive and confidential documents, FIPS 140-2 tokens and token signing are consequently connected.

Note: The stability of the Federation Service depends on the certificates used for token signing. You must back up any certificates specified for this purpose since their loss or unintended removal might cause service disruptions.

Requirements for token-signing certificates

To be compatible with AD FS, a token-signing certificate must fulfill the following conditions:

  • A token-signing certificate must have a private key to sign a security token properly.
  • The private key for the certificate must be accessible to the AD FS service account (Active Directory Federation Service – enables Federated Identity and Access Management by securely sharing digital identity and entitlements rights across security and enterprise boundaries) on the local computer’s store. Setup takes care of this. You can utilize the AD FS Management snap-in to ensure continued access in the event of a certificate change.

Important note: The recommended practice for PKI (public key infrastructure) is not to use the same private key for multiple assignments. Because of this, avoid employing the service communication certificate you deployed on the federation server as the token-signing certificate.

How Partners Utilize Token-Signing Certificates?

Token signing certificates are standard X509 certificates utilized to protectively and securely sign all tokens issued by the federation server. Moreover, any incoming tokens are decrypted using token decryption certificates, which are standard X509 certificates. They are additionally published in federation metadata.

  • Each token-signing certificate comprises public and private cryptographic keys used to digitally sign a security token (using the private key). These keys afterward verify authenticity (using the public key of the encrypted security token) after being received by a partner federation server.
  • The account partner digitally signs each security token, allowing the resource partner to check that the security token was issued by the account partner and had not been altered.
  • The public key section of a partner’s token-signing certificate serves as the verification mechanism for digital signatures. Immediately after the verification of the signature, the resource federation server creates a security token for its organization and signs it using the certificate it has created.
  • Once the certificate has been granted by a CA for federation partner environments, make sure that:
  • Web servers that trust the federation server and dependent parties can access the certificate’s certificate revocation lists (CRLs).
  • Relying parties and Web servers that trust the federation server maintain trust in the root CA certificate.
  • The resource partner’s web server uses the certificate’s public key to check that the resource federation server signed the security token. The client is subsequently given proper access by the web server.

Considerations for Deploying Token-Signing Certificates

The certificate must be obtained and installed in the local computer personal certificate store on the first federation server that is deployed in a new AD FS installation. You can create a self-signed certificate or look for a certificate from an enterprise CA or even a public CA like Certera, Comodo, or Sectigo.

Each federation server in a farm shares a private key from a single token-signing certificate.

  • We suggest all federation servers employ the same certificate in a federation server farm environment. If a CA issues a single certificate tagged as exportable, you can install that certificate on a federation server and export the private key thereafter.
  • All the federation servers in a farm can share the private key from a single token-signing certificate. If you intend to purchase the certificate from a public CA, choosing this option will save you money compared to the “unique token-signing certificate” choice. In conclusion, token signing is an essential procedure in Code Signing Certificates that contributes to the security and trustworthiness of code files. Developers and publishers can maintain the trust and integrity of their code files and resist criminal activity by employing cryptographic tokens and private signing keys.

Understanding YubyKey in Code Signing

A YubiKey is a hardware authentication device. It can be used for two-factor authentication, digital signatures, and password management. For Code Signing, a YubiKey can store the private key of a code signing certificate, allowing it to sign code and software releases physically.

This provides a higher level of security than storing the private key on a device connected to the internet. The YubiKey never exposes the private key externally – it performs the signing process internally and returns only the digital signature. Even if the computer the YubiKey is connected to is compromised, the private key remains secure within the YubiKey.

Code Signing Resources to Understand

Janki Mehta

Janki Mehta

Janki Mehta is a passionate Cyber-Security Enthusiast who keenly monitors the latest developments in the Web/Cyber Security industry. She puts her knowledge into practice and helps web users by arming them with the necessary security measures to stay safe in the digital world.