ateccx08: inttial implementation for ATECCx08

This working implementation for the ATECCx08 family of cryptgraphic processors
has random number generation and other needed supporting functions.

It also includes a sample of how to connect it to the Go crypto/rand package.

More cryptographic functions await a future interation.

Signed-off-by: deadprogram <ron@hybridgroup.com>

examples/ateccx08/lock/main.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"machine"
+
+	"encoding/hex"
+	"time"
+
+	"tinygo.org/x/drivers/ateccx08"
+)
+
+func main() {
+	time.Sleep(5 * time.Second)
+	println("Looking for ATECCx08...")
+
+	machine.I2C0.Configure(machine.I2CConfig{})
+
+	atecc := ateccx08.New(machine.I2C0)
+	atecc.Configure()
+
+	if !atecc.Connected() {
+		for {
+			println("could not connect to ATECCx08")
+			time.Sleep(time.Second)
+		}
+	}
+
+	version, _ := atecc.Version()
+
+	println(version.String(), "started")
+
+	if !atecc.IsLocked() {
+		for i := 10; i > 0; i-- {
+			println(version.String(), "is not locked. Locking in", i, "seconds...")
+			time.Sleep(time.Second)
+		}
+
+		// locks the Configuration zone... PERMANENTLY!
+		atecc.Lock(0)
+	}
+
+	println(version.String(), "locked.")
+
+	for {
+		data, err := atecc.Random()
+		if err != nil {
+			println(err)
+		}
+
+		println(hex.EncodeToString(data[:]))
+		time.Sleep(500 * time.Millisecond)
+	}
+}

examples/ateccx08/random/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"machine"
+
+	"crypto/rand"
+	"encoding/hex"
+	"time"
+
+	"tinygo.org/x/drivers/ateccx08"
+)
+
+var atecc *ateccx08.Device
+
+func main() {
+	time.Sleep(5 * time.Second)
+	println("Looking for ATECCx08...")
+
+	machine.I2C0.Configure(machine.I2CConfig{})
+
+	atecc = ateccx08.New(machine.I2C0)
+	atecc.Configure()
+
+	if !atecc.Connected() {
+		for {
+			println("could not connect to ATECCx08")
+			time.Sleep(time.Second)
+		}
+	}
+
+	version, _ := atecc.Version()
+
+	println(version.String(), "started")
+
+	if !atecc.IsLocked() {
+		for {
+			println(version.String(), "is not locked. Random numbers will not actually be random.")
+			time.Sleep(time.Second)
+		}
+	}
+
+	var result [13]byte
+	for {
+		rand.Read(result[:])
+		encodedString := hex.EncodeToString(result[:])
+		println(encodedString)
+		time.Sleep(500 * time.Millisecond)
+	}
+}

examples/ateccx08/random/rand.go

@@ -0,0 +1,52 @@
+// connects the Go crypto/rand package to the random number generation
+// on the ATECCx08 cryptographic processor.
+package main
+
+import (
+	"crypto/rand"
+	"errors"
+)
+
+var (
+	errNoATECC = errors.New("no ATECCx08")
+)
+
+func init() {
+	rand.Reader = &reader{}
+}
+
+type reader struct{}
+
+func (r *reader) Read(b []byte) (n int, err error) {
+	if len(b) == 0 {
+		return
+	}
+
+	if atecc == nil {
+		return 0, errNoATECC
+	}
+
+	if !atecc.IsLocked() {
+		panic("ATECCx08 is not locked and cannot produce random numbers!")
+	}
+
+	rnds, err := atecc.Random()
+	if err != nil {
+		return 0, err
+	}
+
+	for i := 0; i < len(b); i += 32 {
+		if i+32 > len(b) {
+			copy(b[i:], rnds[:(len(b)-i)])
+			break
+		}
+
+		copy(b[i:], rnds[:])
+		rnds, err = atecc.Random()
+		if err != nil {
+			return 0, err
+		}
+	}
+
+	return len(b), nil
+}