common, crypto: add ICAP functions

2 files changed, 30 insertions, 0 deletions

diff --git a/crypto/key.go b/crypto/key.go
index 35139b67f..4ec43dfd7 100644
--- a/crypto/key.go
+++ b/crypto/key.go
@@ -22,6 +22,7 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"io"
+	"strings"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/pborman/uuid"
@@ -143,3 +144,24 @@ func NewKey(rand io.Reader) *Key {
 
 	return NewKeyFromECDSA(privateKeyECDSA)
 }
+
+// generate key whose address fits into < 155 bits so it can fit into
+// the Direct ICAP spec. for simplicity and easier compatibility with
+// other libs, we retry until the first byte is 0.
+func NewKeyForDirectICAP(rand io.Reader) *Key {
+	randBytes := make([]byte, 64)
+	_, err := rand.Read(randBytes)
+	if err != nil {
+		panic("key generation: could not read from random source: " + err.Error())
+	}
+	reader := bytes.NewReader(randBytes)
+	privateKeyECDSA, err := ecdsa.GenerateKey(S256(), reader)
+	if err != nil {
+		panic("key generation: ecdsa.GenerateKey failed: " + err.Error())
+	}
+	key := NewKeyFromECDSA(privateKeyECDSA)
+	if !strings.HasPrefix(key.Address.Hex(), "0x00") {
+		return NewKeyForDirectICAP(rand)
+	}
+	return key
+}
diff --git a/crypto/key_store_test.go b/crypto/key_store_test.go
index fda87ddc8..de4a21dcf 100644
--- a/crypto/key_store_test.go
+++ b/crypto/key_store_test.go
@@ -20,6 +20,7 @@ import (
 	"encoding/hex"
 	"fmt"
 	"reflect"
+	"strings"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -223,3 +224,10 @@ func loadKeyStoreTestV1(file string, t *testing.T) map[string]KeyStoreTestV1 {
 	}
 	return tests
 }
+
+func TestKeyForDirectICAP(t *testing.T) {
+	key := NewKeyForDirectICAP(randentropy.Reader)
+	if !strings.HasPrefix(key.Address.Hex(), "0x00") {
+		t.Errorf("Expected first address byte to be zero, have: %s", key.Address.Hex())
+	}
+}