LDAPWiki: Digital Signature

Overview [1]#

Digital Signature is a mathematical scheme for demonstrating the Authenticity of a digital message or data.

Digital Signature Algorithms and therefore Digital Signature are not Encryption even though they are Cryptographic Primitives

Digital Signature is the output (hash) of a Cryptographic Hash Function when applied to a stream of data.

A valid Digital Signature for a message sent from Alice gives a Bob a high Level Of Assurance to trust that:

Authentication - the message was created by a known Alice AND
Non-Repudiation - that the Alice cannot deny having sent the message AND
integrity - that the message was not altered in since the Digital Signature was applied AND
Authentication - the message was created by a known Alice (Assumes the recipient has a method to know that Alice is the owner of the Public Key)

Digital Signature are commonly used for Public Key Infrastructure, financial transactions, and in other cases where it is important to detect Authenticity or integrity.[1]

Digital Signatures are based on Public Key cryptography, also known as Asymmetric Key Cryptography

Digital Signatures and Paper Signatures#

Digital Signatures schemes, invented by Diffie-Hellman and formalized by Goldwasser, Micali and Rivest, not only provide the electronic equivalent of signing a paper document with a pen but also are an important building block for many cryptographic protocols such as anonymous voting schemes, e-cash, and Anonymous Credential schemes, to name just a few.

Digital Signature vs. electronic signature#

Unlike Electronic Signatures, Digital Signature employ the use of mathematical algorithms to verify the signer’s identity. Electronic Signatures on the other hand, are simply used to digitally capture a signer’s intent to sign. It may be an electronic mark, symbol, sound or writing.

The major distinction between forms of signature is that digital signatures use a Public Key Infrastructure (PKI) to identify both the individual signing a document and the other party requesting the signature while an Electronic Signature does not.

Of worthy note is that both Electronic Signature and Digital Signature are legally binding. Electronic Signatures are also the most common. Digital signatures are mostly used in critical financial transactions and transactions that need an extra level of confidentiality and security.

Some signing products use both forms when signing a documents.

How Digital Signature works#

Digital Signature requires a Digital Signature Algorithm which includes:

Why Hash Function vs Encryption?#

The reason for encrypting the hash instead of the entire message or document is that a Hash Function can convert a Message into a fixed length value, which is usually much shorter and faster and requires less CPU since hashing is much faster than signing.

Digital Signature Algorithms #

Signatures with efficient protocols #

Signatures with efficient protocols are a form of Digital Signaturee invented by Jan Camenisch and Anna Lysyanskaya in 2001. In addition to being secure digital signatures, they need to allow for the efficient implementation of two protocols

More Information#

There might be more information for this subject on one of the following:

[#1] - Digital Signature - based on information obtained 2013-04-10
[#2] - What Is a Digital Signature and How It Works - based on information obtained 2021-06-17