Secure Element for TLS Version 1.3
draft-urien-tls-se-03

Document Type Active Internet-Draft (individual)
Author Pascal Urien 
Last updated 2021-09-24
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TLS Working Group                                            P. Urien 
  Internet Draft                                          Telecom Paris 
  Intended status: Experimental                                         
                                                                        
                                                      September 24 2021 
  Expires: March 2022 
 
                    Secure Element for TLS Version 1.3 
                         draft-urien-tls-se-03.txt 
    
Abstract 
    
   This draft presents ISO7816 interface for TLS1.3 stack running in 
   secure element. It presents supported cipher suites and key exchange 
   modes, and describes embedded software architecture. TLS 1.3 is the 
   de facto security stack for emerging Internet of Things (IoT) 
   devices. Some of them are constraint nodes, with limited computing 
   resources. Furthermore cheap System on Chip (SoC) components usually 
   provide tamper resistant features, so private or pre shared keys are 
   exposed to hacking. According to the technology state of art, some 
   ISO7816 secure elements are able to process TLS 1.3, but with a 
   limited set of cipher suites. There are two benefits for TLS-SE; 
   first fully tamper resistant processing of TLS protocol, which 
   increases the security level insurance; second embedded software 
   component ready for use, which relieves the software of the burden 
   of cryptographic libraries and associated attacks. TLS-SE devices 
   may also embed standalone applications, which are accessed via 
   internet node, using a routing procedure based on SNI extension. 
    
Requirements Language 
    
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 
   document are to be interpreted as described in RFC 2119. 
    
Status of this Memo 
    
   This Internet-Draft is submitted in full conformance with the 
   provisions of BCP 78 and BCP 79. 
    
   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF). Note that other groups may also distribute 
   working documents as Internet-Drafts. The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/. 
    
   Internet-Drafts are draft documents valid for a maximum of six 
   months and may be updated, replaced, or obsoleted by other documents 
   at any time. It is inappropriate to use Internet-Drafts as reference 
   material or to cite them other than as "work in progress." 
    
   This Internet-Draft will expire on March 2022. 
    

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Copyright Notice 
    
   Copyright (c) 2021 IETF Trust and the persons identified as the 
   document authors. All rights reserved. 
    
   This document is subject to BCP 78 and the IETF Trust's Legal 
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   warranty as described in the Simplified BSD License. 
    
    

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                 Secure Element for TLS Version 1.3      September 2021 
 
Table of Contents 
   Abstract........................................................... 1 
   Requirements Language.............................................. 1 
   Status of this Memo................................................ 1 
   Copyright Notice................................................... 2 
   1 Overview......................................................... 4 
   2 About Secure Elements............................................ 5 
   3 Software components for TLS-SE................................... 5 
      3.1 Cryptographic resources..................................... 6 
      3.2 Data exchange............................................... 6 
          3.2.1 Receiving Record Packet .............................. 6 
          3.2.2 Sending Record Packet ................................ 7 
          3.2.4 RECV and SEND procedure for open application AEAD .... 9 
      3.3 TLS state machine........................................... 9 
      3.4 TLS library................................................ 10 
   4 ISO7816 interface............................................... 11 
   5 ISO 7816 Use Case............................................... 12 
   5 TLS-SE Name..................................................... 14 
   6 Server Name Indication.......................................... 14 
   7 IANA Considerations............................................. 14 
   8 Security Considerations......................................... 14 
   9 References...................................................... 14 
      9.1 Normative References....................................... 14 
      9.2 Informative References..................................... 15 
   10 Authors' Addresses............................................. 15 
 

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1 Overview 
    
   This draft presents ISO7816 interface for TLS1.3 stack running in 
   secure element (see Figure 1), it presents supported cipher suites 
   and key exchange modes, and describes embedded software 
   architecture. TLS 1.3 [RFC8446] is the de facto security stack for 
   emerging Internet of Things (IoT) devices. Some of them are 
   constraint nodes, with limited computing resources. Furthermore 
   cheap System on Chip (SOC) components don't usually provide tamper 
   resistant features, so private or pre shared keys are exposed to 
   hacking. The identity module (im) detailed in [IM] protects identity 
   credentials. The TLS identity module [IM] MAY be based on secure 
   element [ISO7816]. According to the technology state of art, some 
   secure elements are able to process TLS 1.3, but with a limited set 
   of cipher suites. There are two benefits for TLS-SE; first fully 
   tamper resistant processing of TLS protocol, which increases the 
   security level insurance; second embedded software component ready 
   for use, which relieves the software of the burden of cryptographic 
   libraries and associated attacks. 
   Multiple TLS-SE devices, embedding standalone applications, can be 
   hosted by an internet node. In this case SNI extension [RFC6066] MAY 
   be used in order to select the right secure element (see Figure 2). 
    
           +-----------+ recv +------------+ RECV +-----------+ 
           |     IP    + ---> |   TCP/IP   | ---> |  TLS 1.3  | 
           |  Network  +------+ Constraint +------+  Secure   | 
           |           | <--- |    Node    | <--- |  Element  | 
           +-----------+ send +------------+ SEND +-----------+ 
                          |                   | 
                   Network Interface    ISO7816 interface 
    
   Figure 1. TLS 1.3 Secure Element (TLS-SE) 
                                                  +----------+ 
                                                  |  TLS-SE  | 
                                  TLS-SE Name +---+  Secure  | 
                                              |   |  Element | 
                                              |   +----------+ 
                             SNI= TLS-SE Name | 
           +-----------+      +------------+  |   +----------+ 
           |     IP    +      |   TCP/IP   |  |   |  TLS-SE  | 
           |  Network  +------+    Node    +--+---+  Secure  | 
           |           |      |SN Extension|  |   |  Element | 
           +-----------+      +------------+  |   +----------+ 
                                              | 
                                              |   +----------+ 
                                              |   |  TLS-SE  | 
                                  TLS-SE Name +---+  Secure  | 
                                                  |  Element | 
                                                  +----------+ 
    
   Figure 2. Routing procedure based on SNI for TLS-SE devices 

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                 Secure Element for TLS Version 1.3      September 2021 
 
    
2 About Secure Elements 
    
   Secure elements are defined according to [ISO7816] standards. They 
   support hash functions (sha256, sha384, sha512) and associated HMAC 
   procedures. They also provide signatures and DH procedures in Z/pZ* 
   groups, or elliptic curves (for example secp256r1). Open software 
   can be released thanks to JavaCard (JC) standards, such as JC3.04, 
   or JC3.05. Most of secure elements use 8 bits Micro Controller Unit 
   (MCU) and embedded cryptographic accelerator. Non volatile memory 
   size is up to 100KB, and RAM size is up to 10KB. 
    
   Below is an illustration of binary encoding rules for secure element 
   according to the T=0 ISO7816 protocol. 
   An ISO7816 request is a set of bytes comprising a five byte header 
   and an optional payload (up to 255 bytes)  
   The header comprises the following five bytes: 
   - CLA, Class  
   - INS, Instruction code  
   - P1,  P1 byte  
   - P2,  P2 byte  
   - P3,  length of the optional payload, or number of expected bytes 
    
   The response comprises an optional payload (up to 256 bytes) and a 
   two bytes status word (SW1, SW2), SW1=90, SW2=00 (SW=9000) meaning 
   successful operation. 
    
   The ISO7816 defines two main classes for data exchange (called 
   transport protocol), T=0, and T=1. 
   The T=0 transport protocol is a byte stream; a payload can be 
   included in request or response, but not in both. 
   The T=1 transport protocol is a frame stream; payload can be 
   included both in request and response. 
    
3 Software components for TLS-SE 
    
                          +--------+ 
                          | Crypto +----------------+ 
      RECV +----------+   |   Lib  |                | 
      ---> |   Data   |   +--------+     +----------+----------+ 
      <--- | Exchange |        +---------+       TLS Lib       | 
      SEND +----+-----+        |         | Make  Record Packet | 
                |        +-----+-----+   | Check Record Packet | 
                |        | TLS State |   +---------------------+ 
                +--------+  Machine  | 
                         +-----------+ 
    
   Figure 3. Software Components for TLS-SE 
    
    

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3.1 Cryptographic resources 
    
   Many secure elements support hash functions sha256, sha384 and 
   sha512 used by TLS1.3. Associated HMAC, HKDF-Extract and Derive-
   Secret, MUST be implemented by a dedicated cryptographic library. 
    
   Many secure elements support the secp256r1 elliptic curve. Diffie-
   Hellman (DH )calculation are performed according to [IEEE1363] using 
   the ECKAS-DH1 scheme with the identity map as the key derivation 
   function, (KDF), so that the shared secret is the x-coordinate of 
   the ECDH shared secret elliptic curve point represented as an octet 
   string. ECDSA signature is also available for 256,384 and 512 hash 
   size. 
    
   AES-128 is usually implemented, by not AES-CCM. So this AEAD 
   algorithm SHOULD be implemented by a dedicated cryptographic 
   library. 
    
   In summary, according to the state of art TLS-SE supports the 
   secp256r1 EC group, associated ECDSA signature computing and 
   checking, and EC-DHE key establishment. It also implements the AES-
   128-CCM-SHA256 cipher suite. 
    
    
3.2 Data exchange 
    
   TLS record layer packets are received and sent from/to TCP/IP 
   network thanks to well known socket procedures. TLS-SE processes 
   these packets according to a dedicated state machine. 
    
  3.2.1 Receiving Record Packet 
    
   Dedicated ISO7816 requests (named RECV) push incoming record 
   messages in secure element. A fragmentation mechanism splits the 
   record packet in one a several ISO7816 requests, whose payload size 
   is less than 255 bytes. A 2 bits fragmentation-flag field indicates 
   the fragment status; bit F-First notifies the first fragment, and 
   bit F-Last notifies the last fragment. 
    
   The ISO7816 RECV request COULD be encoded as 
   CLA=00, INS=D8, P1=0, P2=fragmentation-flag, P3=fragment-length 
   F-First=b01, F-Last=b10, F-More=b00 
    
   When application AEAD is opened a two bits flag (F-Encrypt, F-
   Decrypt) indicates the cryptographic operation: 
   - P2=b01= F-Decrypt, decryption 
   - P2=b10= F-Encrypt, encryption 
   - P2=b00= Standalone embedded application. 
    
    

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   If F-Last is not set, the ISO7816 response is always 9000 when no 
   error occurs. For the last fragment five cases may occur: 
   - sw-ok: no error, no record message returned, response = 9000. 
   - sw-open, no error, no record message returned, TLS application 
   AEAD is opened, for example response =9001. 
   - sw-close: no error, , no record message returned, TLS application 
   AEAD is closed, for example response =9002 
   - sw-error: error, no record message returned. 
   - sw-more(size): no error, a message or message fragment is ready. 
   For example sw-more(size)= 61xy, in which xy is the size of the 
   first fragment. 
    
                 TCP/IP Node                   Secure Element 
                     |                               | 
                     |-RECV(F-First, Frag#1)-------->| 
                     |<-------------------sw-ok 9000-| 
                     |-RECV(F-More,  Frag#i)-------->| 
                     |<------------------sw-ok= 9000-| 
                     |-RECV(F-Last,  Frag#n)-------->| 
                     |<------------------sw-ok= 9000-| 
                     |<----------------sw-open= 9001-| 
                     |<---------------sw-close= 9002-| 
                     |<----------sw-more(size)= 61xy-| 
    
   Figure 4. Receiving record packet, segmentation mechanism. 
    
  3.2.2 Sending Record Packet 
    
   A sending procedure starts by the reception of a sw-more(size) 
   status, ending a response. This event may occur at the end of RECV 
   procedure (see figure 6) or after TLS state machine reset (see 
   figure 5). 
    
   A RECV(F-First, No-Frag) request resets the TLS state machine. For 
   TLS client a sw-more(size) status is returned. For TLS server the 
   sw-ok status is returned. 
    
       TCP/IP Node                   Secure Element 
           |                               | 
           |-RECV(F-First, No-Frag)------->|=> Reset State Machine 
           |<------------------sw-ok= 9000-| Server 
           |<----------sw-more(size)= 61xy-| Client 
    
   Figure 5. Starting the SEND procedure after RESET request. 
    
       TCP/IP Node                   Secure Element 
           |                               | 
           |-RECV(F-Last, Last-Fragment)-->| => End of Message 
           |<----------sw-more(size)= 61xy-| Client 
    
   Figure 6. Starting SEND procedure after the end of RECV procedure. 

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   The SEND(size) reads a record fragment, whose length is equal to 
   size. It MAY be necessary to adjust the SEND size (see figure 7). 
   Typically at the end of RECV procedure, the size indicated by the 
   sw-more(size) status is an expected fragment length. In that case 
   the status sw-retry status (for example 6Cxy) indicates the fragment 
   size. 
    
       TCP/IP Node                   Secure Element 
           |                               | 
           |-RECV(F-Last, Last-Frag)------>| => End of Message 
           |<----------sw-more(size)= 61xy-| 
           | SEND(size)------------------->| 
           | <------- sw-retry(size')=6Czt-| 
           | SEND(size')------------------>| 
    
   Figure 7. Adjusting SEND size. 
    
   The SEND(size) request is encoded as : 
   CLA=0, INS=C0, P1=0, P2=0, P3=size 
    
   The SEND procedure (see Figure 8) is a set of SEND requests, which 
   read record packet fragments. 
    
    
     TCP/IP Node                            Secure Element 
       |                                          | 
       |<--------------- ---sw-more(size#1)= 61xy-| 
       |-SEND(size#1)---------------------------->| 
       |<---------------Frag#1 || sw-more(size#2)-| 
       |-SEND(size#i)---------------------------->| 
       |<-----------Frag#i || sw-more(size#[i+1])-| 
       |-SEND(size#n)---------------------------->| 
       |<------------------------Frag#n || sw-ok)-|=> SEND End 
       |<------------Frag#n || sw-more(next-size)-|=> SEND Continue 
       |<----------------------Frag#n || sw-open)-|=> Open 
       |<----------------------Frag#n || sw-close-|=> Close 
    
   Figure 8. The SEND procedure 
    
   At the end of SEND procedure four events MAY occur: 
   - End of SEND procedure (status = sw-ok). No more record packets are 
   available. 
   - SEND procedure to be continued (status = sw-more(size)). Another 
   record packet is available. 
   - End of SEND procedure, application AEAD is ready for use (status = 
   sw-open) 
   - End of SEND procedure, application AEAD is closed (status = sw-
   close) 
    
    

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  3.2.4 RECV and SEND procedure for open application AEAD 
    
   When the application AEAD is opened RECV performs decryption and 
   encryption operations (see figure 9). 
    
   For decryption operation (RECV(F-Decrypt)) the RECV procedure pushes 
   the incoming record packet. The returned payload by the SEND 
   procedure is the decrypted message ended by the protocol byte. 
    
   For encryption operation (RECV(F-Encrypt)) the RECV procedure pushes 
   the content to encrypt ended by the associated protocol byte. The 
   returned payload by the SEND procedure is a record packet, including 
   the encrypted content. 
    
    
    TCP/IP Node                                    Secure Element 
       |                                                 | 
       |-RECV(F-First, Frag#1)-------------------------->| 
       |<------------------------------------sw-ok= 9000-| 
       |-RECV(F-More,  Frag#i)-------------------------->| 
       |<------------------------------------sw-ok= 9000-| 
       |-RECV(F-Decrypt/F-Encrypt, F-Last, Frag#n)------>| 
       |<--------------------------sw-more(size#1)= 61xy-| 
       |-SEND(size#1)----------------------------------->| 
       |<----------------------Frag#1 || sw-more(size#2)-| 
       |-SEND(size#i)----------------------------------->| 
       |<------------------Frag#i || sw-more(size#[i+1])-| 
       |-SEND(size#n)----------------------------------->| 
       |<-------------------------------Frag#n || sw-ok)-|=> SEND End 
       |<-----------------------------Frag#n || sw-close-|=> Close 
    
   Figure 9. Decryption/Encryption operations. 
    
    
3.3 TLS state machine 
    
   The state machine manages TLS flights, it determines the next record 
   packet to be received and checked, and the next record packet to be 
   built and sent. The number of states and their order is dependent on 
   the TLS-SE role (client or server), and on the supported working 
   mode (pre shared key, server with certificate, server and client 
   with certificate). Figure 10 details an example of state machine for 
   TLS-SE server, using pre-shared key. The ordered list of states 
   comprises: S-Ready, S-Extensions, S-SFinished, S-ClientCCS, S-
   CFinished and S-Open. 
    

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          TCP/IP Node                   Secure Element 
              |                               | 
              |-RESET------------------------>| 
              |<------------------------sw-ok-| state = S-Ready 
       Client |-RECV(F-First,Frag#1)--------->| 
       Hello  |<------------------------sw-ok-| 
              |-RECV(F-Last,Frag#2)---------->| 
              |                               | Check-ClientHello 
              |                               | Make-ServerHello 
              |<----------------sw-more(size)-| state= S-Extensions 
              |-SEND(size)------------------->| 
       Server |<--------Packet||sw-more(size)-| 
       Hello  |                               | 
              |-SEND(size)------------------->| Make-Extensions 
    Server    |<--------Packet||sw-more(size)-| state= S-SFinished 
    Encrypted |                               | 
    Extension |-SEND(size)------------------->| 
              |                               | Make-ServerFinished 
     Server   |<----------------Packet||sw-ok-| state= S-ClientCCS 
     Finished |                               | 
              |                               | 
    ClientCCS |-RECV(F-First,F-Last,Packet)-->| Check-ClientCCS 
              |<------------------------sw-ok-| state= S-CFinished 
              |                               | 
              |                               | 
    Client    |-RECV(F-First,F-Last,Packet)->-| Check-CFinished 
    Finished  |<----------------------sw-open-| state= S-Open 
              |                               | 
       Packet |-RECV(F-Decrypt,Packet)------->| Decrypt Packet 
              |<----------------sw-more(size)-| Clear Form Message 
              |-SEND(size)------------------->| 
              |<------ -Message||ptcol||sw-ok-| 
              |                               | 
      Message |-RECV(F-Encrypt,Message)------>| Encrypt 
              |<----------------sw-more(size)-| Record Packet 
              |-SEND(size)------------------->| 
              |<------ -Record Packet ||sw-ok-| 
              |                               | 
    
   Figure 10. TLS-SE server with pre-share key state machine 
    
    
3.4 TLS library 
    
   The TLS-SE library is a set of procedures that check, according to 
   the state machine, incoming record packets and build outgoing record 
   packets. In figure 10 the TLS library comprises the following 
   elements: Check-ClientHello, Check-ClientCCS, Check-ClientFinished, 
   Make-ServerHello, Make-EncryptedExensions, and MakeServerFinished. 
    

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4 ISO7816 interface 
    
   The RECV and SEND binary encoding is shown by figure 11 
    
   +------+-----+-----+-------------+-----------+----------+---------+ 
   + name | CLA | INS |      P1     |     P2    |     P3   | Payload | 
   +------+-----+-----+-------------+-----------+----------+---------+ 
   | RECV |  00 |  D8 | 01= Decrypt | 01= First | Fragment |         | 
   |      |           | 02= Encrypt | 02= Last  |  Length  |   Yes   | 
   |      |     |     |             |           | 0= RESET |         | 
   +------+-----+-----+-------------+-----------+----------+---------+ 
   | SEND |  00 |  C0 |     00      |    00     | Incoming |    No   | 
   |      |     |     |             |           |  Length  |         | 
   +------+-----+-----+-------------+-----------+----------+---------+ 
    
   Figure 11. RECV and SEND ISO7816 requests binary encoding 
    
   The status word binary encoding is shown by figure 12. Two binary 
   encoding of sw-more MUST be supported. In the T=0 context, SE 
   operating system returns the 61xy status when a request including a 
   payload, induces a response with a payload. The status 9Fxy is 
   managed by the application in order to notify response size to be 
   returned. The TLS-SE application MAY use 61xy status, but this could 
   induce interoperability issues. 
    
   +----------------+-----+------+ 
   |      name      | SW1 |  SW2 | 
   +----------------+-----+------+ 
   |      sw-ok     |  90 |  00  | 
   +----------------+-----+------+ 
   |  sw-more(size) |  61 | size | 
   |                |  9F | size | 
   +----------------+-----+------+ 
   | sw-retry(size) |  6C + size | 
   +----------------+-----+------+ 
   |    sw-open     |  90 |  01  | 
   +----------------+-----+------+ 
   |    sw-close    |  90 |  02  | 
   +----------------+-----+------+ 
   |    sw-error    |  6D |error | 
   |                |  6F |number| 
   +----------------+-----+------+ 
    
   Figure 12. ISO7816 status word binary encoding 
    

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5 ISO 7816 Use Case 
    
   An open implementation is available at [TLS-SE]. 
    
   Below is an illustration of TLS-SE server, using a pre-shared key 
   (PSK) with DHE over the secp256r1 curve, and the cipher suite AES-
   128-CCM-SHA256. The time consumed by handshake is about 1.4s. 
    
   PSK= 
   0102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F20 
   DHE= 
   037E6E633541EC03DB700A28E7DABB74F8E84D4A28E5F024B46F468A7821305D 
    
   RECV(Client Hello) 
    
   Tx: 00 D8 00 01 F0 16 03 03 00 F2 01 00 00 EE 03 03 
       4E 65 53 05 52 AB 3E 83 14 0B 2F 9C 2F D7 BC 16 
       F9 F5 C4 A9 86 CA 3F C8 8C 6E 8C D1 10 BB B1 57 
       00 00 02 13 04 01 00 00 C3 00 2D 00 03 02 00 01 
       00 2B 00 03 02 03 04 00 0D 00 1E 00 1C 06 03 05 
       03 04 03 02 03 08 06 08 0B 08 05 08 0A 08 04 08 
       09 06 01 05 01 04 01 02 01 00 33 00 47 00 45 00 
       17 00 41 04 9A 1E 0A D8 40 88 D4 21 D1 55 D7 F2 
       8F 78 4C 28 75 F5 19 CA 12 71 96 92 C4 07 8F B4 
       35 42 57 E7 64 24 C1 BC 5D 89 0E F4 08 FD 25 8D 
       24 F4 64 BB C3 F4 80 D3 BF 2C 23 A0 F9 2D A7 88 
       0C 5B 44 53 00 0A 00 06 00 04 00 18 00 17 00 29 
       00 3A 00 15 00 0F 43 6C 69 65 6E 74 5F 69 64 65 
       6E 74 69 74 79 00 00 00 00 00 21 20 CC 05 4A 9F 
       DE 70 E9 96 D6 01 69 61 F5 9A 78 20 D9 FC 6D ED 
       4C C6 0A 7B 0D 
   Rx: 90 00  [47 ms] 
   Tx: 00 D8 00 02 07 4B 68 8F 4E B9 B2 CA 
    
   Rx: 61 86  [879 ms] 
    
   SEND(Server Hello) 
    
   Tx: 00 C0 00 00 86 
   Rx: 16 03 03 00 81 02 00 00 7D 03 03 5C 78 A4 E1 93 
       34 D7 D9 64 B2 85 64 1B E4 76 63 94 39 1F 4A 15 
       27 0A A4 C6 A0 C6 93 D9 E2 16 4D 00 13 04 00 00 
       55 00 29 00 02 00 00 00 33 00 45 00 17 00 41 04 
       25 C9 16 94 8B 39 51 D2 8E 88 70 F7 F5 4E 6C 31 
       62 93 B1 65 55 2C 30 B2 5E 75 6C D8 FE AF DA A7 
       67 D8 AD A7 BE 68 54 EA 3E A0 0B 4D CC 62 93 96 
       38 07 68 29 3E D5 E6 0C 25 4A EA 12 C9 F8 99 7F 
       00 2B 00 02 03 04 9F 1C  [32 ms] 
    
    

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   SEND(Server Encrypted Extensions) 
    
   Tx: 00 C0 00 00 1C 
    
    
   Rx: 17 03 03 00 17 E6 04 4A 52 1A 50 B5 54 D8 73 5E 
       00 F4 FD 66 BB B3 74 50 99 36 C8 08 9F 3A  [78 ms] 
    
   SEND(Server Encrypted Finished) 
    
   Tx: 00 C0 00 00 3A 
    
   Rx: 17 03 03 00 35 CB CA 03 3E E4 34 7E D2 0C 7C 24 
       C1 8F 39 A2 74 39 24 47 78 BE 94 95 7A 31 EC 03 
       D5 0C A8 1C 46 04 05 F2 83 3E 99 0D AD D6 66 63 
       60 23 F8 5D 7B 77 0F 95 18 35 90 00  [185 ms] 
    
   RECV(Client Encrypted Finished) 
    
   Tx: 00 D8 00 03 3A 17 03 03 00 35 BC 29 18 D1 B8 4B 
       C0 3F 6F 81 79 D9 7E FD 58 E3 76 EA 61 13 9C 3E 
       40 0F 34 CD 94 CE C1 44 CB 76 70 7D DA 8A 54 69 
       41 D9 80 CD 5D 52 8F E5 38 D8 52 92 20 54 5E 
   Rx: 90 01  [389 ms] 
    
   TLS13 session is open 
    
   Decryption of incoming Record Packet 
   RECV(Decrypt, Packet) 
   Tx: 00 D8 01 03 24 17 03 03 00 1F 56 E2 D5 B5 C4 A6 
       E2 3E 54 56 5A C4 2D E9 99 F3 58 22 34 15 15 A7 
       96 FD 0E B0 61 60 4C 52 87 
   Rx: 61 0F  [78 ms] 
    
   SEND(Message) 
    
   Tx: 00 C0 00 00 0F 
    
   Rx: 68 65 6C 6C 6F 20 77 6F 72 6C 64 21 0D 0A 17 90 
       00  [15 ms] 
   Rx: hello world! ptcol=17 
    
   Encryption of message 
    
   RECV(Encrypt,Message) 
   Tx: 00 D8 02 03 0F 68 65 6C 6C 6F 20 77 6F 72 6C 64 
       21 0D 0A 17 
    
   Rx: 61 24  [79 ms] 

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   SEND(Record Packet) 
    
   Tx: 00 C0 00 00 24 
   Rx: 17 03 03 00 1F 6F 78 FF 68 0F CA 9E 31 53 2C 96 
       B3 FA D7 B0 51 1B 92 81 35 3D DB FE E9 18 A7 DF 
       36 2F A5 27 90 00  [16 ms] 
    
5 TLS-SE Name 
    
   According to ISO7816 standards, secure elements return upon reset a 
   set of bytes called Answer to Reset (ATR). ATR comprises at least 
   two bytes (TS, T0). The LSB nibble of T0 indicates the number of 
   historical bytes (ranging from 0 to 15). Historical bytes (HB) are 
   located at the end of ATR. Historical bytes can be programmed by 
   standardized API, and therefore MAY be used for secure element 
   naming. 
    
6 Server Name Indication 
    
   According to [RFC6066] Server Name Indication extension is used to 
   route TLS packets toward a virtual host. 
   Multiple TLS-SE devices, embedding standalone applications, can be 
   hosted by an internet node. In this case SNI extension MAY be used 
   in order to select the right secure element, whose name, typically 
   stored in historical bytes, is determined from SNI. 
    
7 IANA Considerations 
    
   This draft does not require any action from IANA. 
    
8 Security Considerations 
    
   This entire document is about security. 
    
9 References 
    
9.1 Normative References 
    
   [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 
   Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 
   https://www.rfc-editor.org/info/rfc8446. 
    
   [RFC6066] Eastlake 3rd, D., "Transport Layer [RFC6066] Security 
   (TLS) Extensions: Extension Definitions", RFC 6066, DOI 
   10.17487/RFC6066, January 2011. 
    
   [ISO7816] ISO 7816, "Cards Identification - Integrated Circuit Cards 
   with Contacts", The International Organization for Standardization 
   (ISO). 
    

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   [IEEE1363] IEEE, "IEEE Standard Specifications for Public Key 
   Cryptography", IEEE Std. 1363-2000, DOI 10.1109/IEEE STD.2000.92292. 
    
9.2 Informative References 
    
   [IM] Urien, P., "Identity Module for TLS Version 1.3", draft-urien-
   tls-im-04.txt, July 2021. 
    
   [TLS-SE] "tls-se.java", https://github.com/purien/TLS-SE 
    
10 Authors' Addresses 
    
   Pascal Urien 
   Telecom Paris 
   19 place Marguerite Perey 
   91120 Palaiseau           Phone: NA 
   France                    Email: Pascal.Urien@telecom-paris.fr 

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