now it can add noise of a laplace distribution

1 files changed, 26 insertions, 2 deletions

diff --git a/diffpriv.go b/diffpriv.go
index 8b945d3..f35dd9a 100644
--- a/diffpriv.go
+++ b/diffpriv.go
@@ -1,19 +1,36 @@
 package main
 
 import (
+	"fmt"
+	"math"
 	"math/rand"
+	"time"
 )
 
+var (
+	rnd = rand.New(rand.NewSource(time.Now().UnixNano()))
+)
+
+func main() {
+	fmt.Println(diffpriv(0, 1, 2))
+}
+
+func diffpriv(value, sensitivity, epsilon float64) float64 {
+	noise := laplaceDist(0, sensitivity/epsilon)
+	fmt.Println("noise: ", noise)
+	return round(float64(value) + noise)
+}
+
 // Returns a random value from a laplace
 // distribution with parameters u and b.
 func laplaceDist(u, b float64) float64 {
-	uniform := rand.Float64()
+	uniform := rnd.Float64()
 	uniform -= 0.5
 	return u - b*sgn(uniform)*math.Log(1-2*math.Abs(uniform))
 }
 
 // The signum function
-func sgn(x float64) flot64 {
+func sgn(x float64) float64 {
 	if x < 0 {
 		return -1
 	}
@@ -22,3 +39,10 @@ func sgn(x float64) flot64 {
 	}
 	return 0
 }
+
+func round(n float64) float64 {
+	if n < 0 {
+		return math.Ceil(n - 0.5)
+	}
+	return math.Floor(n + 0.5)
+}