How Digital Signatures Work
Digital signatures rely on a combination of public key cryptography and hash functions. Here’s a step-by-step breakdown of how the process works:
1. Creating a Hash of the Document
When a user wants to sign a document, the first step is to create a hash of the document. A hash function processes the document and generates a fixed-size string of characters that is unique to the document's content. Even the slightest change in the document will result in a completely different hash.
2. Encrypting the Hash
Once the hash is created, it is encrypted using the sender's private key. This encrypted hash, along with the hashing algorithm used, forms the digital signature. The private key is a part of a key pair, which also includes a public key. The private key is kept secret, while the public key is distributed widely.
3. Attaching the Digital Signature to the Document
The digital signature is then attached to the document. When the recipient receives the document, they can use the sender's public key to decrypt the hash.
4. Verifying the Signature
To verify the signature, the recipient also generates a hash of the received document using the same hashing algorithm. They then compare this hash with the decrypted hash received with the digital signature. If the two hashes match, it confirms that the document has not been altered and that the signature is valid.