diff --git a/ctaphid.c b/ctaphid.c
new file mode 100644
index 0000000..0325cf1
--- /dev/null
+++ b/ctaphid.c
@@ -0,0 +1,109 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "ctaphid.h"
+#include "time.h"
+
+typedef enum
+{
+    IDLE = 0,
+    HANDLING_REQUEST,
+} CTAP_STATE;
+
+static int state;
+static int active_cid;
+static uint64_t active_cid_timestamp;
+static uint8_t ctap_buffer[CTAPHID_BUFFER_SIZE];
+
+void ctaphid_init()
+{
+    state = IDLE;
+    active_cid = 0;
+    active_cid_timestamp = millis();
+}
+
+uint32_t get_new_cid()
+{
+    static uint32_t cid = 1;
+    return cid++;
+}
+
+static int is_broadcast(CTAPHID_PACKET * pkt)
+{
+    return (pkt->cid == CTAPHID_BROADCAST_CID);
+}
+
+static int is_init_pkt(CTAPHID_PACKET * pkt)
+{
+    return (pkt->pkt.init.cmd == CTAPHID_INIT);
+}
+
+static int is_active_cid(CTAPHID_PACKET * pkt)
+{
+    return (pkt->cid == active_cid);
+}
+
+static int is_timed_out()
+{
+    return (millis() - active_cid_timestamp > 500);
+}
+
+
+
+void ctaphid_handle_packet(uint8_t * pkt_raw)
+{
+/*HID_MESSAGE_SIZE*/
+    CTAPHID_PACKET * pkt = (CTAPHID_PACKET *)(pkt_raw);
+
+    printf("Recv packet\n");
+    printf("  CID: %08x\n", pkt->cid);
+    printf("  cmd: %02x\n", pkt->pkt.init.cmd);
+    printf("  length: %d\n", ctaphid_packet_len(pkt));
+
+start_over:
+
+    switch (state)
+    {
+        case IDLE:
+            if (is_broadcast(pkt))
+            {
+                printf("starting a new request\n");
+                state = HANDLING_REQUEST;
+                active_cid = get_new_cid();
+                active_cid_timestamp = millis();
+            }
+            else
+            {
+                printf("Error, unknown request\n");
+            }
+            break;
+        case HANDLING_REQUEST:
+            if (is_active_cid(pkt))
+            {
+                if (is_init_pkt(pkt))
+                {
+                    printf("received abort request from %08x\n", pkt->cid);
+                    ctaphid_init();
+
+                }
+                active_cid_timestamp = millis();
+            }
+            else if (is_timed_out())
+            {
+                ctaphid_init();
+                goto start_over;
+            }
+            else
+            {
+                printf("Too busy with current transaction\n");
+            }
+            break;
+        default:
+            printf("invalid state\n");
+            exit(1);
+    }
+
+}
+
+
+
diff --git a/ctaphid.h b/ctaphid.h
new file mode 100644
index 0000000..8241172
--- /dev/null
+++ b/ctaphid.h
@@ -0,0 +1,47 @@
+#ifndef _CTAPHID_H_H
+#define _CTAPHID_H_H
+
+#include "usbhid.h"
+
+#define TYPE_MASK               0x80    // Frame type mask
+#define TYPE_INIT               0x80    // Initial frame identifier
+#define TYPE_CONT               0x00    // Continuation frame identifier
+
+#define CTAPHID_PING         (TYPE_INIT | 0x01) // Echo data through local processor only
+#define CTAPHID_MSG          (TYPE_INIT | 0x03) // Send U2F message frame
+#define CTAPHID_LOCK         (TYPE_INIT | 0x04) // Send lock channel command
+#define CTAPHID_INIT         (TYPE_INIT | 0x06) // Channel initialization
+#define CTAPHID_WINK         (TYPE_INIT | 0x08) // Send device identification wink
+#define CTAPHID_ERROR        (TYPE_INIT | 0x3f) // Error response
+
+#define CTAPHID_INIT_PAYLOAD_SIZE  (HID_MESSAGE_SIZE-7)
+#define CTAPHID_CONT_PAYLOAD_SIZE  (HID_MESSAGE_SIZE-5)
+
+#define CTAPHID_BROADCAST_CID       0xffffffff
+
+#define CTAPHID_BUFFER_SIZE         4096
+
+typedef struct
+{
+    uint32_t cid;
+    union{
+        struct{
+            uint8_t cmd;
+            uint8_t bcnth;
+            uint8_t bcntl;
+            uint8_t payload[CTAPHID_INIT_PAYLOAD_SIZE];
+        } init;
+        struct{
+            uint8_t seq;
+            uint8_t payload[CTAPHID_CONT_PAYLOAD_SIZE];
+        } cont;
+    } pkt;
+} CTAPHID_PACKET;
+
+void ctaphid_init();
+
+void ctaphid_handle_packet(uint8_t * pkt_raw);
+
+#define ctaphid_packet_len(pkt)     ((uint16_t)((pkt)->pkt.init.bcnth << 8) | ((pkt)->pkt.init.bcntl))
+
+#endif
diff --git a/main.c b/main.c
index 58ccea1..5791755 100644
--- a/main.c
+++ b/main.c
@@ -4,6 +4,7 @@
 
 #include "cbor.h"
 #include "usbhid.h"
+#include "ctaphid.h"
 #include "util.h"
 
 
@@ -18,18 +19,20 @@ void check_ret(CborError ret)
 
 int main(int argc, char * argv[])
 {
-    CborError ret;
-    uint8_t buf[16];
-    memset(buf,0,sizeof(buf));
-    CborEncoder encoder;
-    cbor_encoder_init(&encoder, buf, sizeof(buf), 0);
-    ret = cbor_encode_int(&encoder, 55);
-    check_ret(ret);
+    /*CborError ret;*/
+    /*uint8_t buf[16];*/
+    /*memset(buf,0,sizeof(buf));*/
+    /*CborEncoder encoder;*/
+    /*cbor_encoder_init(&encoder, buf, sizeof(buf), 0);*/
+    /*ret = cbor_encode_int(&encoder, 55);*/
+    /*check_ret(ret);*/
 
-    dump_hex(buf,sizeof(buf));
+    /*dump_hex(buf,sizeof(buf));*/
 
     printf("init usbhid\n");
     usbhid_init();
+    printf("init ctaphid\n");
+    ctaphid_init();
 
     uint8_t hidmsg[64];
     memset(hidmsg,0,sizeof(hidmsg));
@@ -40,6 +43,8 @@ int main(int argc, char * argv[])
     {
         usbhid_recv(hidmsg);
         printf(">> "); dump_hex(hidmsg,sizeof(hidmsg));
+
+        ctaphid_handle_packet(hidmsg);
         printf("<< "); dump_hex(hidmsg,sizeof(hidmsg));
         usbhid_send(hidmsg);
     }
diff --git a/time.c b/time.c
new file mode 100644
index 0000000..a77e4bd
--- /dev/null
+++ b/time.c
@@ -0,0 +1,10 @@
+#include <sys/time.h>
+#include <stdint.h>
+
+uint64_t millis()
+{
+    struct timeval te;
+    gettimeofday(&te, NULL); // get current time
+    uint64_t milliseconds = te.tv_sec*1000LL + te.tv_usec/1000; // calculate milliseconds
+    return milliseconds;
+}
diff --git a/time.h b/time.h
new file mode 100644
index 0000000..41b45e4
--- /dev/null
+++ b/time.h
@@ -0,0 +1,6 @@
+#ifndef _TIME_H
+#define _TIME_H
+
+uint64_t millis();
+
+#endif