diff --git a/.goxc.json b/.goxc.json
index 78c96b2..dd5887c 100644
--- a/.goxc.json
+++ b/.goxc.json
@@ -1,5 +1,5 @@
 {
-	"PackageVersion": "0.0.0",
+	"PackageVersion": "0.0.1",
 	"PrereleaseInfo": "ecrypto",
 	"ConfigVersion": "0.9",
 	"Arch": "386,amd64",
diff --git a/key.go b/key.go
new file mode 100644
index 0000000..aefef4a
--- /dev/null
+++ b/key.go
@@ -0,0 +1,32 @@
+package main
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"errors"
+)
+
+type KeyGenerator struct {
+	publicKey  *PublicKey
+	privateKey *PrivateKey
+}
+
+func (this *KeyGenerator) createRSAKey(size int) error {
+	rsaPrivateKey, err := rsa.GenerateKey(rand.Reader, size)
+	if err != nil {
+		return errors.New("cannot generate the rsa public/private key pair\n" + err.Error())
+	}
+
+	if this.privateKey, err = GetDefaultRSAPrivateKey(rsaPrivateKey); err != nil {
+		return errors.New("cannot generate the rsa public/private key pair\n" + err.Error())
+	}
+	this.publicKey = GetDefaultRSAPublicKey(&rsaPrivateKey.PublicKey)
+	return nil
+}
+
+func (this *KeyGenerator) CreateNewKey(size int, password string) error {
+	if err := this.createRSAKey(size); err != nil {
+		return err
+	}
+	return nil
+}
diff --git a/key_test.go b/key_test.go
new file mode 100644
index 0000000..79df2c0
--- /dev/null
+++ b/key_test.go
@@ -0,0 +1,18 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestCreateRSAKey(t *testing.T) {
+	kc := new(KeyGenerator)
+	if err := kc.createRSAKey(100); err != nil {
+		t.Error(err)
+	}
+	if kc.privateKey == nil {
+		t.Fail()
+	}
+	if kc.publicKey == nil {
+		t.Fail()
+	}
+}
diff --git a/main.go b/main.go
index 52a7925..20bcb9a 100644
--- a/main.go
+++ b/main.go
@@ -2,8 +2,33 @@ package main
 
 import (
 	"fmt"
+	"github.com/codegangsta/cli"
+	"os"
 )
 
+const VERSION = "0.0.1"
+
+var createKeyCommand = cli.Command{
+	Name:  "createkey",
+	Usage: "create a pair of public/private key",
+	Flags: []cli.Flag{
+		cli.IntFlag{Name: "size, s", Value: 2048, Usage: "key size in bits"},
+		cli.StringFlag{Name: "password, p", Value: "", Usage: "password to access the private key"},
+	},
+	Action: func(c *cli.Context) {
+		keyGenerator := new(KeyGenerator)
+		keyGenerator.CreateNewKey(c.Int("size"), c.String("password"))
+	},
+}
+
 func main() {
-	fmt.Println("hello world")
+	app := cli.NewApp()
+	app.Name = "ecrypto"
+	app.Usage = "encrypt files"
+	app.Commands = []cli.Command{
+		createKeyCommand,
+	}
+
+	fmt.Println(os.Args)
+	app.Run(os.Args)
 }
diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..22326b0
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,27 @@
+package main
+
+import (
+	"github.com/codegangsta/cli"
+	"testing"
+)
+
+func TestCreateKeyCommand(t *testing.T) {
+	c := createKeyCommand
+	hasBeenCalled := false
+	c.Action = func(c *cli.Context) {
+		if c.Int("size") != 22 {
+			t.Error("wrong size")
+		}
+		if c.String("password") != "money" {
+			t.Error("wrong password")
+		}
+		hasBeenCalled = true
+	}
+	app := cli.NewApp()
+	app.Commands = []cli.Command{c}
+	args := []string{"file", "createkey", "-size", "22", "-password", "money"}
+	app.Run(args)
+	if !hasBeenCalled {
+		t.Error("sub command *createkey* has not been called")
+	}
+}
diff --git a/marshal.go b/marshal.go
new file mode 100644
index 0000000..f15c21d
--- /dev/null
+++ b/marshal.go
@@ -0,0 +1,72 @@
+package main
+
+import (
+	"crypto/rsa"
+	"math/big"
+)
+
+const (
+	DEFAULT_BLOCK_CYPHER      = "AES"
+	DEFAULT_BLOCK_CYPHER_MODE = "CBC"
+	DEFAULT_HASH_FUNCTION     = "SHA256"
+)
+
+type PrivateKey struct {
+	Name        string
+	Description string
+	Type        string // rsa, el gamal,...
+	Version     string
+	Key         interface{}
+	Accept      *AcceptMethods
+}
+
+type PublicKey struct {
+	Name        string
+	Description string
+	Type        string // rsa, el gamal,...
+	Version     string
+	Key         interface{}
+	Accept      *AcceptMethods
+}
+
+type RSAPublicKey struct {
+	N *big.Int
+	E int
+}
+
+type RSAPrivateKey struct {
+	N *big.Int
+	P *big.Int
+	Q *big.Int
+	D *big.Int
+	E int
+}
+
+type AcceptMethods struct {
+	BlocCypher      string
+	BlockCypherMode string
+	HashFunction    string
+}
+
+func GetDefaultRSAPublicKey(publicKey *rsa.PublicKey) *PublicKey {
+	key := &RSAPublicKey{publicKey.N, publicKey.E}
+	accept := &AcceptMethods{
+		DEFAULT_BLOCK_CYPHER,
+		DEFAULT_BLOCK_CYPHER_MODE,
+		DEFAULT_HASH_FUNCTION,
+	}
+	return &PublicKey{Type: "RSA", Version: VERSION, Key: key, Accept: accept}
+}
+
+func GetDefaultRSAPrivateKey(publicKey *rsa.PrivateKey) (*PrivateKey, error) {
+	if err := publicKey.Validate(); err != nil {
+		return nil, err
+	}
+	key := &RSAPrivateKey{publicKey.N, publicKey.Primes[0], publicKey.Primes[1], publicKey.D, publicKey.E}
+	accept := &AcceptMethods{
+		DEFAULT_BLOCK_CYPHER,
+		DEFAULT_BLOCK_CYPHER_MODE,
+		DEFAULT_HASH_FUNCTION,
+	}
+	return &PrivateKey{Type: "RSA", Version: VERSION, Key: key, Accept: accept}, nil
+}
diff --git a/marshal_test.go b/marshal_test.go
new file mode 100644
index 0000000..c658d35
--- /dev/null
+++ b/marshal_test.go
@@ -0,0 +1,57 @@
+package main
+
+import (
+	"crypto/rsa"
+	"math/big"
+	"testing"
+)
+
+func b(x int64) *big.Int {
+	return big.NewInt(x)
+}
+
+func TestGetDefaultRSAPublicKey(t *testing.T) {
+	key := &rsa.PublicKey{b(31 * 11), 3}
+	pk := GetDefaultRSAPublicKey(key)
+	niceKey, ok := pk.Key.(*RSAPublicKey)
+	if !ok {
+		t.Error("bad key type")
+		return
+	}
+	if big.NewInt(31*11).Cmp(niceKey.N) != 0 {
+		t.Error("bad N")
+	}
+	if 3 != niceKey.E {
+		t.Error("bad e")
+	}
+}
+
+func TestGetDefaultRSAPrivateKey(t *testing.T) {
+	privKey := &rsa.PrivateKey{
+		rsa.PublicKey{b(3 * 11), 7},
+		b(3),
+		[]*big.Int{b(3), b(11)},
+		rsa.PrecomputedValues{},
+	}
+	pk, err := GetDefaultRSAPrivateKey(privKey)
+	if err != nil {
+		t.Error(err)
+	}
+	niceKey, ok := pk.Key.(*RSAPrivateKey)
+	if !ok {
+		t.Error("bad key type")
+		return
+	}
+	if niceKey.D.Int64() != 3 {
+		t.Error("bad D")
+	}
+	if niceKey.E != 7 {
+		t.Error("bad D")
+	}
+	if niceKey.P.Int64() != 3 {
+		t.Error("bad D")
+	}
+	if niceKey.Q.Int64() != 11 {
+		t.Error("bad D")
+	}
+}