diff --git a/csrand.go b/csrand.go
index 4a5cea8..2b8d07e 100644
--- a/csrand.go
+++ b/csrand.go
@@ -10,6 +10,7 @@ type secureRandomSource struct{}
 var RandomSource secureRandomSource
 
 var int63Limit = big.NewInt(0).Lsh(big.NewInt(1), 63)
+var int64Limit = big.NewInt(0).Lsh(big.NewInt(1), 64)
 
 func (_ secureRandomSource) Seed(_ int64) {
 }
@@ -21,3 +22,11 @@ func (_ secureRandomSource) Int63() int64 {
 	}
 	return randNum.Int64()
 }
+
+func (_ secureRandomSource) Uint64() uint64 {
+	randNum, err := crand.Int(crand.Reader, int64Limit)
+	if err != nil {
+		panic(err)
+	}
+	return randNum.Uint64()
+}