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Calcimator

Birthday Attack Calculator

Calculate birthday attack parameters, collision probability, time to collision, and attack feasibility for hash functions.

Inputs

bits

Results

Birthday Bound

400,651,869,298,001,200,000,000,000,000,000,000,000

50% Probability Bound

400,651,869,298,001,200,000,000,000,000,000,000,000

Time to Collision

0 years

Storage Required11,940,356,174,051,796,000,000,000,000,000 GB
Estimated Cost$4,006,518,692,980,011,700,000,000,000,000

Birthday Bound

400,651,869,298,001,200,000,000,000,000,000,000,000

50% Probability Bound

400,651,869,298,001,200,000,000,000,000,000,000,000

Time to Collision

0 years

How to Use This Calculator
  1. Start by filling in the input fields below. Results update instantly as you type, so you can experiment with different values to see how they affect the outcome.
  2. Hash Length — Hash output length in bits Accepts values from 64 bits to 512 bits (default: 256 bits).
  3. Target Collision Probability — Desired probability of finding collision default: 50.
  4. Hash Operations per Second — Computational power available Accepts values from 1,000,000 to 1,000,000,000,000,000 (default: 1,000,000,000).
  5. Once all inputs are set, review your results in the Results panel. Here's what each output means:
  6. Birthday Bound — shown as a numeric value. This is the primary result of this calculator.
  7. 50% Probability Bound — shown as a numeric value. This is the primary result of this calculator.
  8. Time to Collision — shown as a numeric value. This is the primary result of this calculator.
  9. Storage Required — shown as a numeric value.
  10. Estimated Cost — shown as a dollar amount.
  11. Explore the related calculators below if you need deeper analysis or want to approach this topic from a different angle.
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Formula

Birthday Bound ≈ √(2 × m × ln(1/(1-P)))

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