Base-N Keyspace Equivalence Compare
Signed log2 keyspace difference between independent uniform alphabet models; not actual password entropy.
Description
Compare nominal alphabet-and-length keyspaces using their signed log2 difference.
An alphabet and fixed length define a nominal keyspace only when symbols are chosen independently and uniformly. Comparing its logarithm avoids constructing very large integer counts.
When to use this tool
Compare nominal alphabet-and-length keyspaces using their signed log2 difference. Use it when the input measurements and conventions below match the operation you need.
- Prepare alphabetA, lengthA, alphabetB, lengthB, 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.
Alphabet sizes must be integers from 2 to one million, and lengths integers from zero to one million. The returned bit difference is length A times log2(alphabet A) minus length B times log2(alphabet B). A positive value means a larger modeled space for A.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| alphabetA | Alphabet a. | Integer; from 2 to 1000000 inclusive |
| lengthA | Length a. | Integer; from 0 to 1000000 inclusive |
| alphabetB | Alphabet b. | Integer; from 2 to 1000000 inclusive |
| lengthB | Length b. | Integer; from 0 to 1000000 inclusive |
| Output field | Interpretation |
|---|---|
| result | Object containing the following named result fields. |
| result.signedBitsDifference | Signed bits difference; use the stated units and sign convention. |
{
"input": {
"alphabetA": 16,
"lengthA": 2,
"alphabetB": 2,
"lengthB": 8
},
"output": {
"result": {
"signedBitsDifference": 0
}
}
}Limitations and assumptions
- The result is keyspace equivalence under the stated model, not measured password entropy. Biased choices, restrictions, dictionaries and attack costs are not included.
- 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
- keyspace size calculator
A fixed-length keyspace has A choices at each of L positions when every position can use the same alphabet independently.
- letter frequency rank compare
Letter-frequency ranking depends on the submitted sample and expected ordering.