Add ephemeral ID code

go.mod

@@ -4,6 +4,8 @@ require (
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/pkg/errors v0.9.1
 	github.com/spf13/jwalterweatherman v1.1.0
+	gitlab.com/xx_network/crypto v0.0.4
+	golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad
 )
 
 go 1.13

go.sum

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@@ -11,16 +36,91 @@ github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrk
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+honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
+honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

id/ephemeral/id.go

+package ephemeral
+
+import (
+	"crypto"
+	"encoding/binary"
+	"github.com/pkg/errors"
+	"gitlab.com/xx_network/crypto/large"
+	"gitlab.com/xx_network/primitives/id"
+	"math"
+	"time"
+)
+
+var period = int64(time.Hour * 24)
+var numOffsets int64 = 1 << 16
+
+// Ephemeral ID type alias
+type Id uint64
+
+// GetId returns ephemeral ID based on passed in ID
+func GetId(id *id.ID, size uint) (Id, error) {
+	iid, err := GetIntermediaryId(id)
+	if err != nil {
+		return math.MaxUint64, err
+	}
+	return GetIdFromIntermediary(iid, size)
+}
+
+// GetIntermediaryId returns an intermediary ID for ephemeral ID creation (ID hash)
+func GetIntermediaryId(id *id.ID) ([]byte, error) {
+	b2b := crypto.BLAKE2b_256.New()
+	_, err := b2b.Write(id.Marshal())
+	if err != nil {
+		return nil, err
+	}
+	idHash := b2b.Sum(nil)
+	return idHash, nil
+}
+
+// GetIdFromIntermediary returns the ephemeral ID from intermediary (id hash)
+func GetIdFromIntermediary(iid []byte, size uint) (Id, error) {
+	b2b := crypto.BLAKE2b_256.New()
+	if size > 64 {
+		return math.MaxUint64, errors.New("Cannot generate ID with size > 64")
+	}
+	salt := getRotationSalt(iid)
+
+	_, err := b2b.Write(iid)
+	if err != nil {
+		return math.MaxUint64, err
+	}
+	_, err = b2b.Write(salt)
+	if err != nil {
+		return math.MaxUint64, err
+	}
+	eid := b2b.Sum(nil)
+	return Id(large.NewIntFromBytes(eid).Uint64()), nil
+}
+
+// getRotationSalt returns rotation salt based on ID hash and timestamp
+func getRotationSalt(idHash []byte) []byte {
+	hashNum := large.NewIntFromBytes(idHash)
+	offset := large.NewInt(1).Mod(hashNum, large.NewInt(numOffsets)).Int64()
+	ts := time.Now().UnixNano()
+	timestampPhase := ts % period
+	var saltNum uint64
+	if timestampPhase < offset {
+		saltNum = uint64((ts - period) / period)
+	} else {
+		saltNum = uint64(ts / period)
+	}
+	salt := make([]byte, 8)
+	binary.BigEndian.PutUint64(salt, saltNum)
+	return salt
+}

id/ephemeral/id_test.go

+package ephemeral
+
+import (
+	"gitlab.com/xx_network/primitives/id"
+	_ "golang.org/x/crypto/blake2b"
+	"testing"
+)
+
+// Unit test for GetId
+func TestGetId(t *testing.T) {
+	testId := id.NewIdFromString("zezima", id.User, t)
+	eid, err := GetId(testId, 99)
+	if err == nil {
+		t.Error("Should error with size > 64")
+	}
+	eid, err = GetId(testId, 28)
+	if err != nil {
+		t.Errorf("Failed to create ephemeral ID: %+v", err)
+	}
+	t.Log(eid)
+}