45cc676f55
- pkg/types/chunk.go: shared Chunk struct breaking engine<->sources circular import - pkg/engine/finding.go: Finding struct with MaskKey for pipeline output - pkg/engine/entropy.go: Shannon entropy function using math.Log2 - pkg/engine/entropy_test.go: TDD tests for Shannon and MaskKey
24 lines
502 B
Go
24 lines
502 B
Go
package engine
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import "math"
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// Shannon computes the Shannon entropy of a string in bits per character.
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// Returns 0.0 for empty strings.
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// A value >= 3.5 indicates high randomness, consistent with real API keys.
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func Shannon(s string) float64 {
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if len(s) == 0 {
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return 0.0
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}
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freq := make(map[rune]float64)
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for _, c := range s {
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freq[c]++
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}
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n := float64(len([]rune(s)))
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var entropy float64
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for _, count := range freq {
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p := count / n
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entropy -= p * math.Log2(p)
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}
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return entropy
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}
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