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In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfect number. The next perfect number is 28, since 1 + 2 + 4 + 7 + 14 = 28.
So, 6 is a perfect number because the proper divisors of 6 are 1, 2, and 3, and 1 + 2 + 3 = 6. [2] [4] Euclid proved c. 300 BCE that every Mersenne prime M p = 2 p − 1 has a corresponding perfect number M p × (M p +1)/2 = 2 p − 1 × (2 p − 1). For example, the Mersenne prime 2 2 − 1 = 3 leads to the corresponding perfect number 2 2 − ...
5 Analytic number theory: additive problems. ... Computational number theory is also known as algorithmic number theory. ... Almost perfect number; Amicable number;
In mathematics, a multiply perfect number (also called multiperfect number or pluperfect number) is a generalization of a perfect number. For a given natural number k , a number n is called k -perfect (or k -fold perfect) if the sum of all positive divisors of n (the divisor function , σ ( n )) is equal to kn ; a number is thus perfect if and ...
The Millionaires' problem is an important problem in cryptography, the solution of which is used in e-commerce and data mining. Commercial applications sometimes have to compare numbers that are confidential and whose security is important. Many solutions have been introduced for the problem, including physical solutions based on cards. [1]
This is an accepted version of this page This is the latest accepted revision, reviewed on 7 January 2025. Practice and study of secure communication techniques "Secret code" redirects here. For the Aya Kamiki album, see Secret Code. "Cryptology" redirects here. For the David S. Ware album, see Cryptology (album). This article needs additional citations for verification. Please help improve ...
For example, in the Diffie–Hellman key exchange, an eavesdropper observes and exchanged as part of the protocol, and the two parties both compute the shared key . A fast means of solving the DHP would allow an eavesdropper to violate the privacy of the Diffie–Hellman key exchange and many of its variants, including ElGamal encryption .
Furthermore, this problem is random self-reducible, which ensures that for a given N, every public key is just as secure as every other public key. The GM cryptosystem has homomorphic properties , in the sense that if c 0 , c 1 are the encryptions of bits m 0 , m 1 , then c 0 c 1 mod N will be an encryption of m 0 ⊕ m 1 {\displaystyle m_{0 ...