feat: impl. new protol design & new head

internal/algo/key.go

@@ -0,0 +1,40 @@
+package algo
+
+import (
+	"encoding/binary"
+	"math/bits"
+	"math/rand"
+)
+
+func RandKeyIndex() uint8 {
+	return uint8(rand.Intn(32))
+}
+
+func MixKeys(k1, k2 []byte) []byte {
+	if len(k1) != 32 || len(k2) != 32 {
+		panic("unexpected key len")
+	}
+	k := make([]byte, 64)
+	for i := range k1 {
+		k1i, k2i := i, 31-i
+		k1v, k2v := k1[k1i], k2[k2i]
+		binary.LittleEndian.PutUint16(
+			k[i*2:(i+1)*2],
+			expandkeyunit(k1v, k2v),
+		)
+	}
+	return k
+}
+
+func expandkeyunit(v1, v2 byte) (v uint16) {
+	v1s, v2s := uint16(v1), uint16(bits.Reverse8(v2))
+	for i := 0; i < 8; i++ {
+		v |= v1s & (1 << (i * 2))
+		v1s <<= 1
+	}
+	for i := 0; i < 8; i++ {
+		v2s <<= 1
+		v |= v2s & (2 << (i * 2))
+	}
+	return
+}