Signing & Verifying Text

Digital signatures, much like their analog counterparts, serve as a method for asserting the authenticity and integrity of a digital document or message. However, unlike traditional signatures, digital signatures offer a much higher level of security, making it possible to ascertain not only the identity of the signer but also whether the content has been tampered with since it was signed.

The foundation of digital signing and verification lies in the field of public key cryptography, a cornerstone of modern secure communication. This system relies on two keys: a private key, which is kept secret by the owner, and a public key, which can be shared with anyone. To sign a document, the signer uses their private key to generate a digital signature on the document. This signature is unique to both the document and the private key, ensuring that any changes made to the document after it has been signed can be detected.

Verification, on the other hand, requires the corresponding public key. When a document is received along with its digital signature, the recipient can use the signer’s public key to verify the signature. This process checks that the signature matches the document and was created with the private key corresponding to the public key. If the document has been altered after signing, the verification will fail, alerting the recipient to the tampering.

One of the advantages of digital signatures is the ability to use multiple private keys for signing a document, similar to having a document signed by multiple parties. Each signer uses their private key to sign the document, and each signature can be independently verified with the corresponding public key. This method is particularly useful in scenarios requiring the approval or authorization of multiple entities.

Digital signatures are a critical component of secure communications, providing assurances of authenticity, integrity, and non-repudiation. Non-repudiation means that a signer cannot later deny the authenticity of the signature on a document they signed. This is especially important in legal, financial, and sensitive communications, where trust and authenticity are paramount.

Tools like GpgFrontend facilitate the process of creating and verifying digital signatures in a user-friendly manner. GpgFrontend is built on top of the OpenPGP standard, which is a widely accepted protocol for encryption and digital signatures. The tool allows users to easily manage their encryption keys, sign documents, and verify the signatures of received documents, thereby enhancing the security and trustworthiness of digital communications.

In summary, digital signing and verification through tools like GpgFrontend leverage public key cryptography to ensure the security and integrity of digital communications. By enabling users to sign documents with their private keys and allowing others to verify those signatures with corresponding public keys, digital signatures provide a robust mechanism for authenticating the origin and integrity of digital documents, far surpassing the capabilities of traditional handwritten signatures.

Signature Only

By signing the text, you establish that you are the sole and unalterable authority for this text. You can simply sign the text without encrypting it as follows:

To check whether a key can be used for signing, please review the ‘Usage’ column in the key toolbox on the right (the letter ‘S’ stands for signature).

Signature with Encryption

You also have the option to sign and encrypt at the same time by choosing a public key for encryption and your private key for signing. This is a common practice where you select two key pairs: one belonging to someone else for encryption, and your private key for signing. If you don’t select a key for signing, only encryption is possible, but you will receive a warning. It’s worth noting that combining signing with encryption provides an additional layer of security as it assures the recipient that the message hasn’t been altered and it came from the sender whose identity is verified by the digital signature.

Verification

Once you have a plaintext and its corresponding signature, you can verify the signature using the signer’s public key. However, this type of signature isn’t suitable for emails as it can make the email less readable.

To verify a signature with text, you need to have the corresponding public key for all included signatures. If a suitable public key for a signature isn’t found locally during verification, GpgFrontend will prompt you to import it.

Verification with Decryption

When decrypting a ciphertext, it’s advised to verify it simultaneously, regardless of whether the encryptor signed it or not. It’s impossible to determine from the ciphertext’s format if it has been signed. Therefore, it’s a good habit to always perform decryption operations with verification whenever possible.