Salt Uniqueness Bits Rule of Thumb
Minimum salt bits under union-bound birthday probability; independent uniform salts assumed, not entropy certification.
Description
Estimate minimum random-salt bits for a chosen union-bound collision probability.
Independently generated random salts can collide when many records share a finite salt space. This calculator sizes that space against a caller-selected upper bound on collision probability using a pair-count bound.
When to use this tool
Estimate minimum random-salt bits for a chosen union-bound collision probability. Use it when the input measurements and conventions below match the operation you need.
- Prepare records, maximumCollisionProbability, respecting the measurement basis and boundaries below.
- Compare the worked example with your intended operation before reusing its result.
How to use the tool and how it works
- Enter every field in the input table using the stated units and exact supported selector spelling where applicable.
- Run the tool. Correct input errors before interpreting an output.
- Read the result fields below; use accompanying flags and the stated sign, boundary or model convention when interpreting a number.
records must be an integer from 2 to one billion and the target probability strictly between zero and one. Required bits are max(0, ceil(log2(n) plus log2(n minus 1) minus 1 minus log2(p))). This makes n(n minus 1)/(2 times 2^bits) no greater than the requested bound.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| records | Records. | Integer; from 2 to 1000000000 inclusive |
| maximumCollisionProbability | Maximum collision probability. | Finite number |
| Output field | Interpretation |
|---|---|
| result | Object containing the following named result fields. |
| result.unionBoundMinimumBits | Union bound minimum bits; use the stated units and sign convention. |
{
"input": {
"records": 1000,
"maximumCollisionProbability": 0.000001
},
"output": {
"result": {
"unionBoundMinimumBits": 39
}
}
}Limitations and assumptions
- The result assumes uniform independent salts and uses a union bound, not an exact collision probability. It does not measure random-generator quality, password entropy or compliance with a password-storage standard.
- Every declared field is required and unexpected fields are rejected. Numeric inputs must be finite; input errors are distinct from a valid false result or an explicitly qualified output.
- Extremely large inputs and nonfinite or excessively large outputs are rejected. List positions reported by the tool use zero-based indices unless stated otherwise.
Alternative or Complementary methods
Use the applicable protocol specification and a reviewed implementation for real verification, hashing or key management. A format label, probability model or tentative text mapping does not replace that operation. Compare the scope of the nearby tools below before substituting one.
References
Similar or alternative tools
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