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p2p/discover: new distance metric based on sha3(id)

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The previous metric was pubkey1^pubkey2, as specified in the Kademlia
paper. We missed that EC public keys are not uniformly distributed.
Using the hash of the public keys addresses that. It also makes it
a bit harder to generate node IDs that are close to a particular node.
This commit is contained in:
Felix Lange
2015-04-27 00:50:18 +02:00
parent d457a1187d
commit 2adcc31bb4
6 changed files with 354 additions and 106 deletions
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22
p2p/discover/node_test.go
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@ -9,6 +9,7 @@ import (
"testing/quick"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto"
)
@ -169,7 +170,7 @@ func TestNodeID_pubkeyBad(t *testing.T) {
}
func TestNodeID_distcmp(t *testing.T) {
distcmpBig := func(target, a, b NodeID) int {
distcmpBig := func(target, a, b common.Hash) int {
tbig := new(big.Int).SetBytes(target[:])
abig := new(big.Int).SetBytes(a[:])
bbig := new(big.Int).SetBytes(b[:])
@ -182,15 +183,15 @@ func TestNodeID_distcmp(t *testing.T) {
// the random tests is likely to miss the case where they're equal.
func TestNodeID_distcmpEqual(t *testing.T) {
base := NodeID{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
x := NodeID{15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0}
base := common.Hash{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
x := common.Hash{15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0}
if distcmp(base, x, x) != 0 {
t.Errorf("distcmp(base, x, x) != 0")
}
}
func TestNodeID_logdist(t *testing.T) {
logdistBig := func(a, b NodeID) int {
logdistBig := func(a, b common.Hash) int {
abig, bbig := new(big.Int).SetBytes(a[:]), new(big.Int).SetBytes(b[:])
return new(big.Int).Xor(abig, bbig).BitLen()
}
@ -201,19 +202,19 @@ func TestNodeID_logdist(t *testing.T) {
// the random tests is likely to miss the case where they're equal.
func TestNodeID_logdistEqual(t *testing.T) {
x := NodeID{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
x := common.Hash{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}
if logdist(x, x) != 0 {
t.Errorf("logdist(x, x) != 0")
}
}
func TestNodeID_randomID(t *testing.T) {
func TestNodeID_hashAtDistance(t *testing.T) {
// we don't use quick.Check here because its output isn't
// very helpful when the test fails.
for i := 0; i < quickcfg.MaxCount; i++ {
a := gen(NodeID{}, quickrand).(NodeID)
dist := quickrand.Intn(len(NodeID{}) * 8)
result := randomID(a, dist)
a := gen(common.Hash{}, quickrand).(common.Hash)
dist := quickrand.Intn(len(common.Hash{}) * 8)
result := hashAtDistance(a, dist)
actualdist := logdist(result, a)
if dist != actualdist {
@ -224,6 +225,9 @@ func TestNodeID_randomID(t *testing.T) {
}
}
// TODO: this can be dropped when we require Go >= 1.5
// because testing/quick learned to generate arrays in 1.5.
func (NodeID) Generate(rand *rand.Rand, size int) reflect.Value {
var id NodeID
m := rand.Intn(len(id))