Back

Digital Signatures

Next

Restart

Next

This work is licensed with a Creative Commons Attribution 4.0 International LicenseEndFragment

1/8

Digital Signatures

Encryption

Bob’s Public Key

The objective of a digital signature is to authenticate and verify documents and data to avoid tampering and digital modification or forgery during the transmission. A digital signature uses the public key cryptography architecture. Typically, an asymmetric key system encrypts using a public key and decrypts with the private key. For digital signatures, however, the reverse is true. The sender encrypts the signature using a private key and the receiver decrypts with the corresponding public key. Because the keys are linked, decrypting with the public key verifies that the proper private key signed the document, thereby verifying the signature’s provenance. 

SignedContract

Contract

Decryption

2/8

Bob’s Private Key

Store Keys

Generate RSA KeysPublic Key: Private Key:

Private Key

PKI Server

3/8

Public Key

Bob has a public and a private key. The public key is typically stored on a public key infrastructure server. A public key can be given to anyone, like Alice, whom Bob needs to communicate with. Bob stores his private key locally on his system.

Digital signatures use a cryptographic hash. A fixed-size string of bytes of the document is generated using a hash function.  Hashing algorithms include SHA-1 (a 160-bit hash value), SHA-256 and SHA-3 (a 256-bit hash value). MD5 produces a 128-bit hash value, but it is now considerred insecure due to vulnerabilties. 

How Does a Digital Signature Work?

Bob needs to send Alice several documents. Since the documents are not confidential, Bob does not need to encrypt them, but Alice will need to verify that these documents came from Bob, and that they were not modified during transit.

To simulate this step, enter a message no longer than 15 characters.

Step 1: The documents are passed to a hash function to create a hash digest.

4/8

Enter Message (max 15 characters): Generate SHA-256 Hash SHA-256 Hash:

Click to begin the digital signature process

In addition to asymmetric encryption, digital signatures use a cryptographic hash. A fixed-size string of bytes of the document is generated using a hash function.  Hashing algorithms include SHA-1 (a 160-bit hash value), SHA-256 and SHA-3 (a 256-bit hash value). MD5 produces a 128-bit hash value, but it is now considerred insecure due to vulnerabilties. 

5/8

Step 2: The hash digest gets encrypted with Bob’s private key. 

Step 3: Alice receives the reports and the encrypted hash. She can decrypt the hash with Bob’s public key availble from the PKI server.

6/8

#

7/8

Step 4: Alice will pass the reports through the same hash algorithm to generate a hash digest. If the hashes match, it verifies data integrity.

Since the hashes match, Alice knows that Bob used his private key to encrypt the hash to secure the signature.

Digital Signature: High legal recognition  

Technology

Electronic Signature: Varies by method and evidence  

Legal Recognition

Digital Signature: High security, encryption

Security

Electronic Signature: Varies by method

Use Cases

Digital Signature: Authenticity, integrity, non-repudiation

Digital Signature: Official documents, contracts

Electronic Signature: Show intent or agreement

Electronic Signature: Business documents, online agreements

Digital Signature: Cryptographic algorithms, key pairs  

Digital signatures and electronic signatures are both methods used to authenticate and verify the integrity of digital documents, but they serve different purposes and are based on different technologies.An electronic signature is a broader term that refers to any electronic process that indicates acceptance of an agreement or a record. It can be as simple as a typed name, a clicked checkbox, or a handwritten signature on a touchscreen.                                                 Click on each button to learn more.

8/8

Electronic Signature: Touchscreens, click-to-sign, biometrics  

Purpose