What is Digital Signature Algorithm (DSA)?

In this post titled ”What is Digital Signature Algorithm (DSA)?”, we would look at digital signature algorithm’s importance, history of DSA, DSA vs. RSA, Key generation, and lots more

The Digital Signature Algorithm (DSA) is a signature technique, not an encryption algorithm, that generates digital signatures using public-key cryptography.

About Digital Signature Algorithm (DSA)

The National Institute of Standards and Technology created the Digital Signature Algorithm (DSA) (NIST). The complexity of computing discrete logarithms is the basis for the algorithm.

During the 1990s, the US government developed DSA. It is a signature algorithm, not an encryption technique, and it generates digital signatures using public-key cryptography.

Based on the mathematical notion of modular exponentiation and the discrete logarithm problem, the Digital Signature Algorithm (DSA) is a Federal Information Processing Standard for digital signatures. The DSA signature system is a combination of the Schnorr and ElGamal signature techniques.

DSA was proposed by the National Institute of Standards and Technology (NIST) for use in their Digital Signature Standard (DSS) in 1991, and it was adopted as FIPS 186 in 1994.
There have been four updates to the original specification. FIPS 186-4, published in July 2013, is the most recent specification.

DSA is protected by a patent, but NIST has made it royalty-free around the world. A draft version of the specification FIPS 186-5 implies DSA will no longer be authorised for digital signature generation. But may be used to confirm signatures created prior to the implementation date of that standard.

Digital Signature Algorithms: A Beginner’s Guide

History of DSA

The United States government issued a request for suggestions for a public key signature standard in 1982. The National Institute of Standards and Technology (NIST) suggested DSA as a component of their Digital Signature Standard in August 1991. (DSS). There was a lot of backlash at first, notably from software businesses that had already spent time and money developing digital signature software based on the RSA cryptosystem.

Despite this, the National Institute of Standards and Technology (NIST) approved DSA as a Federal standard (FIPS 186) in 1994. The initial specification has been revised four times: In 1998, the Federal Information Processing Standard (FIPS) 186–1 was published.

In 2000, FIPS 186–2, FIPS 186–3, and FIPS 186–4 were issued, respectively.

Signing with DSA is prohibited in a draft version of FIPS 186-5. However signatures generated before to the standard’s implementation date as a document can be verified. It will be phased out in favor of newer signature methods like EdDSA.

DSA is protected by U.S. Patent 5,231,668, which was issued on July 26, 1991 but has since expired and is credited to David W. Kravitz, a former NSA employee. This patent was granted to “The United States of America as represented by the Secretary of Commerce, Washington, D.C.,” and NIST has made it royalty-free for everyone across the world.

Claus P. Schnorr makes a claim that his now-expired U.S. Patent 4,995,082 covered DSA; however, this claim is debatable.


Key creation (which forms the key pair), key distribution, signing, and signature verification are all part of the DSA algorithm.

Key generation

This has two phase. The first phase involves selecting algorithm parameters that can be shared among system users. While the second phase involves computing a single key pair for a single user.

For creating an electronic signature for diverse applications, DSA (Digital Signature Algorithm) utilizes the algebraic features of discrete logarithm problems and modular exponentiations. NIST (National Institute of Standards and Technology) approved it as a Federal Information Processing Standard in 1994.

To construct the digital fingerprint, most digital signature creation algorithms use the standard tactic of signing the message digest (hash of the actual message) with the source private key.

However, DSA is unusual in that it generates two signatures by combining two difficult and distinct signing and verification procedures.
As a result, the DSA method is more than just using private and public keys at the beginning and end of a connection.

The Digital Signature Algorithm: An Overview

Digital signatures are created using a variety of algorithms. The majority of them use a basic way of signing message digests with the sender’s private keys. This is how the data is sent’s digital thumbprint is created.

Please keep in mind that the message digest, not the data, is signed.

As a result, the signature is quite modest. The digital signature algorithm, on the other hand, does not work in this way. When employing DSA, the technique is more complicated than simply using a private and public key at the beginning and end of the transmission, accordingly.

On the other hand, it uses sophisticated and unique mathematical functions to generate two digital signatures, which we will learn more about in the following sections of this article.

As far as I can tell, DSA is only used to generate signatures. They can’t be utilized to encrypt information. As a result, it is not subject to the typical import and export restrictions that apply to RSA.

The Digital Signature Algorithm in Action (DSA)

The DSA algorithm is a digital signature standard that is based on the public-key cryptosystems principle. And is based on the algebraic features of discrete logarithm problems and modular exponentiations.

Digital signatures are based on the concept of two cryptographic keys that are mutually authenticating. Public/private key pairs are used to create signatures. A mathematically connected private key and public key can be created using a public-key algorithm like RSA. With his private key, one can sign a digital message.

A private key can be used to encrypt data relating to signatures. A person who wants to make a digital signature should always have their private key with them. Because the public and private keys are mathematically connected, they can always be deduced from one another. The only way to decrypt this data is to use the signer’s public key. Anyone who requires verification of the signer’s signature can be given the public key. It is critical to keep your private key confidential because it can be used to generate your signature on a document. The authentication digital signature is completed in this manner. Only public and private keys ensure the validity of a digital signature.

The digital signature algorithm, on the other hand, does not encrypt data with a private key.

A public key is also used to decrypt the data in a digital signature process. DSA uses the notion of a unique mathematical function to construct a digital signature with two 160-bit values. The private key and the message digest are used to generate these two integers.

The verification method is complicated since the public key is not utilized to authenticate the signature. For added protection, both keys are utilized to safeguard data in a particular digital signature algorithm.

The message digest is now created using a hash function. The digital signature is created using the produced message digest and the DSA algorithm. The message is then sent with this signature attached. The same hash algorithm is used to authenticate the source and data on the receiving end.

  • With the assistance of the key generation algorithm, keys are generated. To sign a document, created keys are utilized.
  • A digital signature algorithm is used to generate a signature.
  • A message digest is created using a hash function.
  • The digital signature is provided by the message digest with DSA.
  • After that, the digital signature is transferred together with the data.
  • Verification is used to verify the signature’s authenticity algorithms. The same hash function is used for verification.

Digital Signature Algorithm’s Importance

Because of the ever-increasing cyber risks, it is vital to identify and verify the owner’s authenticity anytime a user sends data over the internet. We must guarantee that the document owner is trustworthy and that no changes were made during transfer.

Digital signatures are electronic signatures that allow the recipient to verify the message’s authenticity. DSA is one of the algorithms that can be used to create these electronic signatures. In DSA, the sender creates a digital signature and attaches it to the message so that anyone on the receiving end may verify it.

DSA provides the following advantages:

  • Non-repudiation: the sender cannot argue that the data was not sent after signature verification.
  • Integrity: Data change during transmission hinders message decryption or final verification.
  • Message Authentication: Using the proper private/public key pair, you can authenticate the sender’s identity.

DSA consists of three steps:

  • Create a key pair as the initial step.
  • Signing a message is the next step.
  • The message’s signature is verified in the third phase.

A private key and a public key make up a DSA key pair. The public key can be shared with anybody, while the private key is produced at random and kept hidden. The private key must be known by the person creating the signature in order to sign a message However, the public key matching to the private key used to generate the signature is all that is required to verify a message signed with a DSA signature.

A digital signature is a mathematical system that proves that digital messages or documents are genuine. A valid digital signature verifies that the message came from a known sender (authentication) and that it was not tampered with during transmission (integrity). Modern computer security and commerce rely heavily on digital signatures.

The digital signature of messages can be generated using the DSA method. It’s usually used in tandem with other security protocols like PGP or SSL/TLS. Some cryptographic nonce algorithms and key exchange protocols employ it as well.

To protect conversations over the internet, it employs mathematical functions and a set of keys.

The private key is used to sign messages, while the public key is used to verify the authenticity of those signatures. Digital signatures are more authentic when two distinct keys are used.

The DSA technique is based on the ElGamal signature scheme, which was invented in 1985 although it functions and secures data in a very different way. For creating keys and signing data, the DSA technique requires a random number generator. Whereas ElGamal does not. ElGamal does not state that a message should not be signed more than once or with distinct keys, like the DSA algorithm does.

Digital Signature Algorithm (DSA) Benefits

  • In addition to having high strength levels, the signature is shorter than other digital signature standards.
  • The computing speed of signatures is slower.
  • When compared to other digital standards, DSA requires less storage to function.
  • Because DSA is patent-free, it can be used for free.
  • A digital signature is a method through which the message’s author can ensure that the message has not been tampered with after it has been signed. The user is additionally protected from falsification by the signature.
  • Asymmetric key cryptography is used. As a result, no further asymmetric key cryptography will be required. DSA is thus faster than other methods such as RSA.
  • It utilizes less memory than other techniques because the signature is generated using only a 160-bit hash value.

Digital Signature Algorithm Disadvantages

• It takes a long time to authenticate since the verification method involves sophisticated residual operators. The computing process takes a long time.

• DSA does not encrypt data. In this case, we can just authenticate data.

• The digital signature algorithm computes and signs the SHA1 hash first. Any flaws in SHA1’s cryptographic security are mirrored in DSA because it is implicitly reliant on it.

• DSA is a US National Standard that can be used in both secret and non-secret communications.

Additional Information on the Digital Signature Algorithm (DSA)

A standard for digital signatures is referred to as a digital signature algorithm (DSA). The National Institute of Standards and Technology (NIST) first announced it in 1991 as a better way to create digital signatures.
DSA, along with RSA, is one of the most widely used digital signature algorithms today.
Most digital signature types, unlike DSA, are created by signing message digests with the originator’s private key. This gives the data a digital thumbprint. The signature is often significantly smaller than the data that was signed because just the message digest is signed.

As a result, digital signatures put less strain on processors during the signing process, consume less bandwidth, and produce minimal amounts of ciphertext for cryptanalysis.

DSA, on the other hand, does not encrypt or decrypt message digests using a private key or a public key. Instead, it creates a digital signature consisting of two 160-bit values derived from the message digests and the private key using unique mathematical functions. When compared to RSA, DSAs employ the public key to authenticate the signature. But the authentication method is more difficult.

The digital signature processes for RSA and DSA are commonly thought to be equivalent in strength. DSAs are normally not subject to import or export restrictions, which are often imposed on RSA cryptography. Because they are only used for digital signatures and have no mechanisms for encrypting data.

How does the algorithm verify the sender’s identity?

The DSA algorithm uses a systematic calculation mechanism to generate a hash value and a digital signature from the message digest and the private key, which are two 160-bit values. The signature is non-deterministic due to the randomization. It authenticates signatures via a public key, which is far more complicated than RSA.

To finish the procedure, the DSA cycle follows these three main steps:

• Key Generation: To obtain private (x) and public (y) keys that satisfy the mathematical constraints of 0 x q and y = gx mod p, the procedure uses the notion of modular exponentiation. Where q is a prime divisor, p is a prime number, and g meets the requirements gq mod p = 1 and gh**((p–1)/q) mod p. As a result, the private and public key packages p,q,g,x and p,q,g,y are created.

• Signature Generation: A hashing algorithm provides a message digest, which is passed as an input to a signing function, which generates two variable outputs, r and s, packaged as signature r,s, and transmitted to the recipient as a bundle with the message and these variables.

• Signature Verification: The method outputs the digest using the hashing function, and the verification component v is created by combining variable s with additional parameters from the key generation stage. The verification function compares the generated variable v to the M,s,r bundle’s parameter r.

Non-mathematically, here’s how you summarize the following process:
  • To sign the document, you use the key generation algorithm to generate keys.
  • • The signature is then generated using a digital signature technique.
  • Create a message digest using a hash function, then combine it with DSA to create a digital signature.
  • Enclose the signature with the data so that the receiver may verify it.
  • A verification algorithm is used by the recipient to verify the signature. It’s the hash function that was utilized to make the message digest before.

The Advantages of Using the Digital Signature Algorithm

  • Requires less storage space for the entire procedure
  • Fast signature computation
  • Freely available (patent-free) for use everywhere in the world.
  • Signatures are short.
  • Real-time observation
  • It is non-intrusive
  • For legal compliance, DSA is widely recognised around the world.
  • It saves time (low time consumption in comparison to processes of physical signing etc.)

The disadvantages of employing the Digital Signature Algorithm

  • The underlying cryptography must be fresh to assure its strength, and the process does not involve key exchange capabilities.
  • Due to DSA’s second authentication standard, the standardization of computer hardware and software vendors on RSA may cause problems.
  • The complex remainder operations require a lot of time for computation and thus signature verification.
  • Because the technique does not encrypt the data, it merely assures authentication, not confidentiality.
  • To construct the message digest, DSA methods compute the SHA1 hash. As a result, it reflects all of the SHA1 hash function’s weaknesses in the algorithm.

DSA vs. RSA: Which is Better?

The Digital Signature Technique is an asymmetric key encryption algorithm used by government entities in the United States for secret and non-secret communication. RSA is a public-key cryptography algorithm that uses modular arithmetic to secure communication and digital signatures. Its strength is based on the problem of prime number factorization. As a result, unlike other encryption methods such as RSA, DSA is solely used for digital signatures.

Despite the fact that they use distinct mathematical procedures, the cryptography strength is the same. The speed, performance, and support for the SSH protocol are the primary differences between the two algorithms.

• RSA is slower than DSA in terms of decryption, key generation, and verification. But it is fast in terms of encryption and signature. Authentication, on the other hand, necessitates both, and speed differences are minor in real-world applications.

• Support for the Secure Shell network protocol is another difference. RSA supports both the old SSH and the more secure SSH2, but DSA only supports SSH2.

Using DSA, authenticate the data source.

To build a safe and secure environment in today’s linked world, digital signatures are required. They’re an excellent technique to verify any record over the internet.

The article provides an overview of the Digital Signature algorithms, including advantages, weaknesses, security constraints, and a comparison to RSA.

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