It has taken over two decades to establish and secure the current ecommerce applications. The security of most of these systems principally relies on cryptographic algorithms which have served the purpose till now. Since the initiation and evolution of quantum computing, some cryptographic algorithms have threats. To mitigate the security gap, numerous postquantum algorithms have been proposed. This article enlightens the journey towards postquantum algorithms and security parameters of the newly proposed postquantum algorithms.
Current crypto implementations and application
The process of system digitalization across the world started from early ’90s and has been quite mature till today such as DRM, secure email and web servers etc. Cryptocurrencies such as BitCoin have become famous since the last decade. Symmetric (3DES, AES, Blowfish etc), Asymmetric (RSA, DSA, ElGamal, DiffieHellman and ECC etc) and hash (SHA256, RIPEMD and Whirlpool) cryptographic algorithms have been comprehensively incorporated for the security of these business applications. The security of these algorithms is based on the fact that the brute force attack (attempt all potential keys) is not possible due to the current limited computational power and time constraints.
Threats to current crypto applications from quantum computing
As of late, there has been generous research on quantum PCs for the resolution of complex mathematics problems which are intractable for traditional computing platforms. The formalization of such quantum computing platforms will pose serious threats to the following categories of cryptographic algorithms:

Symmetric and Hash Algorithms: The main threat to the security of symmetric and hash algorithms is Grover’s algorithm which provisions to enhance the speed of brute force or exhaustive key search attack on the algorithms in such a way that the key length is reduced to 50%. It reciprocates that the strength of 128bit AES and 256bit hash will be reduced to 64bit AES and 128bit hash respectively. The best countermeasure to the quantum threats will be to double the key length of symmetric and hash algorithms making them safe against the attacks by quantum computers.

Asymmetric Algorithms: Asymmetric algorithms such as RSA and ECC are based on hard math problems such as integer factorization problem, Discrete Logarithm Problem (DLP) Elliptic Curve DLP. These problems ensure it is computationally impossible to factor large integers and the private key/secret cannot be deduced from the public key/secret. The core threat to the security of asymmetric algorithms is Shor’s Algorithm which modestly expedites and accelerates the mathematical calculations to break currently in use asymmetric algorithms.
Need for postquantum algorithms
As a consequence of security threats posed to RSA and ECC algorithms, National Institute of Standards and Technology (NIST) have started the process of standardization of postquantum or quantum resistant algorithms.
The ultimate aim of postquantum cryptography is to design cryptographic algorithms which are unbreakable by highly powerful quantum computational platforms.
NIST has released the Round 2 submissions (26 algorithms) for evaluation and comments/feedback from the general public cryptographers and information security experts.
It includes seventeen (17) Publickey Encryption/Keyestablishment algorithms and nine (09) Digital Signature algorithms.
Security of postquantum algorithms
In the field of crypto algorithm design, it is mandatory to elaborate that the security of an algorithm is proportional to a very difficult mathematical issue/problem. Presently the research in the field of postquantum cryptography is predominantly to find hard problems in the following 05 areas/domains:

Latticebased Cryptography: deals with the design of asymmetric algorithms based on lattice creation or the hard math problems related to lattices such as Short Vector Problem (SVP), GapSVP, Closest Vector Problem (CVP), GapCVP and Shortest independent Vectors Problem (SIVP) etc

Multivariate Cryptography: deals with the design of asymmetric algorithms based on multivariate polynomials scattered over a finite field. The proposed algorithms are based on the NP (nondeterministic polynomialtime) hard problems

Hashbased Cryptography: involves the design of asymmetric algorithms based on security parameters of hash functions such as incorporating onetime signature with Merkle tree and onetime key pairs.

Codebased Cryptography: is based on the algorithms on the basis of errorcorrecting codes, which are eventually based on NPhard problems.

Supersingular elliptic curve isogeny Cryptography: is based on the algorithms designed on the hard problems of supersingular elliptic curves dealing with endomorphism rings.
The list of Postquantum Public key algorithms (NIST Round 2 Submissions) and their corresponding categories are as follows:
Sr. No 
Public Key Algorithm 
Category 
1. 
BIKE 
Codebased Cryptography 
2. 
Classic McEliece 
Codebased Cryptography 
3. 
CRYSTALSKYBER 
Latticebased Cryptography 
4. 
FrodoKEM 
Latticebased Cryptography 
5. 
HQC 
Codebased Cryptography 
6. 
LAC 
Latticebased Cryptography 
7. 
LEDAcrypt 
Codebased Cryptography 
8. 
NewHope 
Latticebased Cryptography 
9. 
NTRU 
Latticebased Cryptography 
10. 
NTRU Prime 
Latticebased Cryptography 
11. 
NTSKEM 
Codebased Cryptography 
12. 
ROLLO 
Codebased Cryptography 
13. 
Round5 
Latticebased Cryptography 
14. 
RQC 
Codebased Cryptography 
15. 
SABER 
Latticebased Cryptography 
16. 
SIKE 
Supersingular elliptic curve isogeny Cryptography 
17. 
Three Bears 
Latticebased Cryptography 
The list of Postquantum Digital Signature algorithms (Round 2 Submissions) and their corresponding categories are as follows:
Sr. No 
Digital Signature Algorithm 
Category 
1. 
CRYSTALSDILITHIUM 
Latticebased Cryptography 
2. 
FALCON 
Latticebased Cryptography 
3. 
GeMSS 
Multivariate Cryptography 
4. 
LUOV 
Multivariate Cryptography 
5. 
MQDSS 
Multivariate Cryptography 
6. 
Picnic 
Zero Knowledge Proof 
7. 
qTESLA 
Lattice Cryptography 
8. 
Rainbow 
Multivariate Cryptography 
9. 
SPHINCS+ 
Hashbased Cryptography 
Cryptoagility and quantum computing
Cryptoagility is mentioned as a distinction of a secure system to modestly switch over to substitute (secure) cryptographic primitives and algorithms. NIST process/path of standardization of postquantum algorithms will lead to crypto agility. As soon as the postquantum algorithms are standardized and published, organizations will start incorporating them in their products so that customer can switch over to the secure ones in case of algorithm break/compromise ensuring/achieving cryptoagility.
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