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Fast Modular Exponential Calculator

Binary Exponentiation Formula:

\[ a^b \mod m = \text{result of binary exponentiation algorithm} \]

integer
integer
integer

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1. What Is Binary Exponentiation?

Binary exponentiation (also known as exponentiation by squaring) is an efficient algorithm for computing large exponents modulo a number. It reduces the time complexity from O(n) to O(log n), making it essential for cryptographic applications and large number computations.

2. How Does The Calculator Work?

The calculator uses the binary exponentiation algorithm:

\[ a^b \mod m = \text{result computed through iterative squaring and multiplication} \]

Algorithm Steps:

  1. Initialize result = 1
  2. Reduce base modulo modulus: base = base % modulus
  3. While exponent > 0:
    • If exponent is odd: result = (result * base) % modulus
    • Exponent = exponent / 2 (integer division)
    • Base = (base * base) % modulus

3. Importance Of Modular Exponentiation

Details: Modular exponentiation is fundamental in public-key cryptography (RSA, Diffie-Hellman), primality testing, and various number theory applications. Its efficiency makes secure digital communications possible.

4. Using The Calculator

Tips: Enter integer values for base, exponent, and modulus. The modulus must be a positive integer greater than 0. The calculator efficiently computes even very large exponents.

5. Frequently Asked Questions (FAQ)

Q1: Why use binary exponentiation instead of direct computation?
A: Direct computation becomes infeasible for large exponents due to enormous intermediate values. Binary exponentiation handles large numbers efficiently.

Q2: What is the time complexity of this algorithm?
A: O(log n), where n is the exponent, making it exponentially faster than naive approaches.

Q3: Can this handle negative exponents?
A: This implementation handles non-negative exponents only. For negative exponents, modular inverses would be needed.

Q4: What are the practical applications?
A: Cryptography, computer algebra systems, computational number theory, and anywhere large modular exponentiations are required.

Q5: Are there limitations to this algorithm?
A: The algorithm assumes integer inputs and may have precision limitations with extremely large numbers in some implementations, though PHP handles big integers well.

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