draft-ietf-lwig-security-protocol-comparison-01.txt   draft-ietf-lwig-security-protocol-comparison-02.txt 
Network Working Group J. Mattsson Network Working Group J. Mattsson
Internet-Draft F. Palombini Internet-Draft F. Palombini
Intended status: Informational Ericsson AB Intended status: Informational Ericsson AB
Expires: January 3, 2019 July 2, 2018 Expires: July 6, 2019 January 2, 2019
Comparison of CoAP Security Protocols Comparison of CoAP Security Protocols
draft-ietf-lwig-security-protocol-comparison-01 draft-ietf-lwig-security-protocol-comparison-02
Abstract Abstract
This document analyzes and compares per-packet message size overheads This document analyzes and compares per-packet message size overheads
when using different security protocols to secure CoAP. The analyzed when using different security protocols to secure CoAP. The analyzed
security protocols are DTLS 1.2, DTLS 1.3, TLS 1.2, TLS 1.3, and security protocols are DTLS 1.2, DTLS 1.3, TLS 1.2, TLS 1.3, and
OSCORE. DTLS and TLS are analyzed with and without 6LoWPAN-GHC OSCORE. DTLS and TLS are analyzed with and without 6LoWPAN-GHC
compression. DTLS is analyzed with and without Connection ID. compression. DTLS is analyzed with and without Connection ID.
Status of This Memo Status of This Memo
skipping to change at page 1, line 34 skipping to change at page 1, line 34
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This Internet-Draft will expire on January 3, 2019. This Internet-Draft will expire on July 6, 2019.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Overhead of Security Protocols . . . . . . . . . . . . . . . 3 2. Overhead of Security Protocols . . . . . . . . . . . . . . . 2
2.1. DTLS 1.2 . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. DTLS 1.2 . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1. DTLS 1.2 . . . . . . . . . . . . . . . . . . . . . . 3 2.1.1. DTLS 1.2 . . . . . . . . . . . . . . . . . . . . . . 3
2.1.2. DTLS 1.2 with 6LoWPAN-GHC . . . . . . . . . . . . . . 4 2.1.2. DTLS 1.2 with 6LoWPAN-GHC . . . . . . . . . . . . . . 3
2.1.3. DTLS 1.2 with Connection ID . . . . . . . . . . . . . 4 2.1.3. DTLS 1.2 with Connection ID . . . . . . . . . . . . . 4
2.1.4. DTLS 1.2 with Connection ID and 6LoWPAN-GHC . . . . . 5 2.1.4. DTLS 1.2 with Connection ID and 6LoWPAN-GHC . . . . . 5
2.2. DTLS 1.3 . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2. DTLS 1.3 . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2.1. DTLS 1.3 . . . . . . . . . . . . . . . . . . . . . . 6 2.2.1. DTLS 1.3 . . . . . . . . . . . . . . . . . . . . . . 5
2.2.2. DTLS 1.3 with 6LoWPAN-GHC . . . . . . . . . . . . . . 6 2.2.2. DTLS 1.3 with 6LoWPAN-GHC . . . . . . . . . . . . . . 6
2.2.3. DTLS 1.3 with Connection ID . . . . . . . . . . . . . 7 2.2.3. DTLS 1.3 with Connection ID . . . . . . . . . . . . . 6
2.2.4. DTLS 1.3 with Connection ID and 6LoWPAN-GHC . . . . . 7 2.2.4. DTLS 1.3 with Connection ID and 6LoWPAN-GHC . . . . . 7
2.2.5. DTLS 1.3 with Short Header . . . . . . . . . . . . . 8 2.3. TLS 1.2 . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2.6. DTLS 1.3 with Short Header and 6LoWPAN-GHC . . . . . 8 2.3.1. TLS 1.2 . . . . . . . . . . . . . . . . . . . . . . . 7
2.3. TLS 1.2 . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3.2. TLS 1.2 with 6LoWPAN-GHC . . . . . . . . . . . . . . 8
2.3.1. TLS 1.2 . . . . . . . . . . . . . . . . . . . . . . . 9 2.4. TLS 1.3 . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.2. TLS 1.2 with 6LoWPAN-GHC . . . . . . . . . . . . . . 9 2.4.1. TLS 1.3 . . . . . . . . . . . . . . . . . . . . . . . 8
2.4. TLS 1.3 . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.4.2. TLS 1.3 with 6LoWPAN-GHC . . . . . . . . . . . . . . 9
2.4.1. TLS 1.3 . . . . . . . . . . . . . . . . . . . . . . . 10 2.5. OSCORE . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4.2. TLS 1.3 with 6LoWPAN-GHC . . . . . . . . . . . . . . 10 3. Overhead with Different Parameters . . . . . . . . . . . . . 11
2.5. OSCORE . . . . . . . . . . . . . . . . . . . . . . . . . 11 4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3. Overhead with Different Parameters . . . . . . . . . . . . . 12 5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15 7. Informative References . . . . . . . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 15
7. Informative References . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
This document analyzes and compares per-packet message size overheads This document analyzes and compares per-packet message size overheads
when using different security protocols to secure CoAP over UPD when using different security protocols to secure CoAP over UPD
[RFC7252] and TCP [RFC8323]. The analyzed security protocols are [RFC7252] and TCP [RFC8323]. The analyzed security protocols are
DTLS 1.2 [RFC6347], DTLS 1.3 [I-D.ietf-tls-dtls13], TLS 1.2 DTLS 1.2 [RFC6347], DTLS 1.3 [I-D.ietf-tls-dtls13], TLS 1.2
[RFC5246], TLS 1.3 [I-D.ietf-tls-tls13], and OSCORE [RFC5246], TLS 1.3 [I-D.ietf-tls-tls13], and OSCORE
[I-D.ietf-core-object-security]. The DTLS and TLS record layers are [I-D.ietf-core-object-security]. The DTLS and TLS record layers are
analyzed with and without compression. DTLS is anlyzed with and analyzed with and without compression. DTLS is anlyzed with and
without Connection ID [I-D.ietf-tls-dtls-connection-id] and DTLS 1.3 without Connection ID [I-D.ietf-tls-dtls-connection-id]. Readers are
is analyzed with and without the use of the short header. Readers expected to be familiar with some of the terms described in RFC 7925
are expected to be familiar with some of the terms described in RFC [RFC7925], such as ICV.
7925 [RFC7925], such as ICV.
2. Overhead of Security Protocols 2. Overhead of Security Protocols
To enable comparison, all the overhead calculations in this section To enable comparison, all the overhead calculations in this section
use AES-CCM with a tag length of 8 bytes (e.g. AES_128_CCM_8 or AES- use AES-CCM with a tag length of 8 bytes (e.g. AES_128_CCM_8 or AES-
CCM-16-64), a plaintext of 6 bytes, and the sequence number '05'. CCM-16-64), a plaintext of 6 bytes, and the sequence number '05'.
This follows the example in [RFC7400], Figure 16. This follows the example in [RFC7400], Figure 16.
Note that the compressed overhead calculations for DLTS 1.2, DTLS Note that the compressed overhead calculations for DLTS 1.2, DTLS
1.3, TLS 1.2 and TLS 1.3 are dependent on the parameters epoch, 1.3, TLS 1.2 and TLS 1.3 are dependent on the parameters epoch,
skipping to change at page 6, line 14 skipping to change at page 5, line 39
When compressed with 6LoWPAN-GHC, DTLS 1.2 with the above parameters When compressed with 6LoWPAN-GHC, DTLS 1.2 with the above parameters
(epoch, sequence number, Connection ID, length) gives 17 bytes (epoch, sequence number, Connection ID, length) gives 17 bytes
overhead. overhead.
2.2. DTLS 1.3 2.2. DTLS 1.3
2.2.1. DTLS 1.3 2.2.1. DTLS 1.3
This section analyzes the overhead of DTLS 1.3 [I-D.ietf-tls-dtls13]. This section analyzes the overhead of DTLS 1.3 [I-D.ietf-tls-dtls13].
The changes compared to DTLS 1.2 are: omission of version number, The changes compared to DTLS 1.2 are: omission of version number,
merging of epoch and sequence number fields (of total 8 bytes) into merging of epoch into the first byte containing signalling bits,
one 4-bytes-field. optional omission of length, reduction of sequence number into a 1 or
2-bytes field.
DTLS 1.3 record layer (22 bytes, 16 bytes overhead): In this example, the length field is omitted, and the 1-byte field is
17 40 00 00 05 00 0f ae a0 15 56 67 92 ec 4d ff used for the sequence number. The minimal DTLSCiphertext structure
8a 24 e4 cb 35 b9 is used (see Figure 4 of [I-D.ietf-tls-dtls13]).
Content type: DTLS 1.3 record layer (17 bytes, 11 bytes overhead):
17 21 05 ae a0 15 56 67 92 ec 4d ff 8a 24 e4 cb 35 b9
Epoch and sequence:
40 00 00 05 First byte (including epoch):
Length: 21
00 0f Sequence number:
05
Ciphertext (including encrypted content type): Ciphertext (including encrypted content type):
ae a0 15 56 67 92 ec ae a0 15 56 67 92 ec
ICV: ICV:
4d ff 8a 24 e4 cb 35 b9 4d ff 8a 24 e4 cb 35 b9
DTLS 1.3 gives 16 bytes overhead. DTLS 1.3 gives 11 bytes overhead.
2.2.2. DTLS 1.3 with 6LoWPAN-GHC 2.2.2. DTLS 1.3 with 6LoWPAN-GHC
This section analyzes the overhead of DTLS 1.3 [I-D.ietf-tls-dtls13] This section analyzes the overhead of DTLS 1.3 [I-D.ietf-tls-dtls13]
when compressed with 6LoWPAN-GHC [RFC7400] [OlegHahm-ghc]. when compressed with 6LoWPAN-GHC [RFC7400] [OlegHahm-ghc].
Note that this header compression is not available when DTLS is used Note that this header compression is not available when DTLS is used
over transports that do not use 6LoWPAN together with 6LoWPAN-GHC. over transports that do not use 6LoWPAN together with 6LoWPAN-GHC.
Compressed DTLS 1.3 record layer (23 bytes, 17 bytes overhead): Compressed DTLS 1.3 record layer (18 bytes, 12 bytes overhead):
02 17 40 80 12 05 00 0f ae a0 15 56 67 92 ec 4d 11 21 05 ae a0 15 56 67 92 ec 4d ff 8a 24 e4 cb
ff 8a 24 e4 cb 35 b9 35 b9
Compressed DTLS 1.3 record layer header and nonce: Compressed DTLS 1.3 record layer header and nonce:
02 17 40 80 12 05 00 0f 11 21 05
Ciphertext (including encrypted content type): Ciphertext (including encrypted content type):
ae a0 15 56 67 92 ec ae a0 15 56 67 92 ec
ICV: ICV:
4d ff 8a 24 e4 cb 35 b9 4d ff 8a 24 e4 cb 35 b9
When compressed with 6LoWPAN-GHC, DTLS 1.3 with the above parameters When compressed with 6LoWPAN-GHC, DTLS 1.3 with the above parameters
(epoch, sequence number, length) gives 17 bytes overhead. (epoch, sequence number, no length) gives 12 bytes overhead.
2.2.3. DTLS 1.3 with Connection ID 2.2.3. DTLS 1.3 with Connection ID
This section analyzes the overhead of DTLS 1.3 [I-D.ietf-tls-dtls13] This section analyzes the overhead of DTLS 1.3 [I-D.ietf-tls-dtls13]
with Connection ID [I-D.ietf-tls-dtls-connection-id]. with Connection ID [I-D.ietf-tls-dtls-connection-id].
DTLS 1.3 record layer (23 bytes, 17 bytes overhead): In this example, the length field is omitted, and the 1-byte field is
17 40 00 00 05 42 00 0f ae a0 15 56 67 92 ec 4d used for the sequence number. The minimal DTLSCiphertext structure
ff 8a 24 e4 cb 35 b9 is used (see Figure 4 of [I-D.ietf-tls-dtls13]), with the addition of
the Connection ID field.
Content type: DTLS 1.3 record layer (18 bytes, 12 bytes overhead):
17 31 42 05 ae a0 15 56 67 92 ec 4d ff 8a 24 e4 cb 35 b9
Epoch and sequence:
40 00 00 05 First byte (including epoch):
31
Connection ID: Connection ID:
42 42
Length: Sequence number:
00 0f 05
Ciphertext (including encrypted content type): Ciphertext (including encrypted content type):
ae a0 15 56 67 92 ec ae a0 15 56 67 92 ec
ICV: ICV:
4d ff 8a 24 e4 cb 35 b9 4d ff 8a 24 e4 cb 35 b9
DTLS 1.3 gives 17 bytes overhead. DTLS 1.3 with Connection ID gives 12 bytes overhead.
2.2.4. DTLS 1.3 with Connection ID and 6LoWPAN-GHC 2.2.4. DTLS 1.3 with Connection ID and 6LoWPAN-GHC
This section analyzes the overhead of DTLS 1.3 [I-D.ietf-tls-dtls13] This section analyzes the overhead of DTLS 1.3 [I-D.ietf-tls-dtls13]
with Connection ID [I-D.ietf-tls-dtls-connection-id] when compressed with Connection ID [I-D.ietf-tls-dtls-connection-id] when compressed
with 6LoWPAN-GHC [RFC7400] [OlegHahm-ghc]. with 6LoWPAN-GHC [RFC7400] [OlegHahm-ghc].
Note that this header compression is not available when DTLS is used Note that this header compression is not available when DTLS is used
over transports that do not use 6LoWPAN together with 6LoWPAN-GHC. over transports that do not use 6LoWPAN together with 6LoWPAN-GHC.
Compressed DTLS 1.3 record layer (24 bytes, 18 bytes overhead): Compressed DTLS 1.3 record layer (19 bytes, 13 bytes overhead):
02 17 40 80 13 05 42 00 0f ae a0 15 56 67 92 ec 12 31 05 42 ae a0 15 56 67 92 ec 4d ff 8a 24 e4
4d ff 8a 24 e4 cb 35 b9 cb 35 b9
Compressed DTLS 1.3 record layer header and nonce: Compressed DTLS 1.3 record layer header and nonce:
02 17 40 80 13 05 42 00 0f 12 31 05 42
Ciphertext (including encrypted content type): Ciphertext (including encrypted content type):
ae a0 15 56 67 92 ec ae a0 15 56 67 92 ec
ICV: ICV:
4d ff 8a 24 e4 cb 35 b9 4d ff 8a 24 e4 cb 35 b9
When compressed with 6LoWPAN-GHC, DTLS 1.3 with the above parameters When compressed with 6LoWPAN-GHC, DTLS 1.3 with the above parameters
(epoch, sequence number, Connection ID, length) gives 18 bytes (epoch, sequence number, Connection ID, no length) gives 13 bytes
overhead. overhead.
2.2.5. DTLS 1.3 with Short Header
This section analyzes the overhead of DTLS 1.3 with short header
format [I-D.ietf-tls-dtls13]. The short header format for DTLS 1.3
reduces the header of 5 bytes, by omitting the length value and
sending 1 lower bit of epoch value instead of 2, and 12 lower bits of
sequence number instead of 30.
DTLS 1.3 record layer (17 bytes, 11 bytes overhead):
30 05 ae a0 15 56 67 92 ec 4d ff 8a 24 e4 cb 35
b9
Short epoch and sequence:
30 05
Ciphertext (including encrypted content type):
ae a0 15 56 67 92 ec
ICV:
4d ff 8a 24 e4 cb 35 b9
DTLS 1.3 with short header gives 11 bytes overhead.
2.2.6. DTLS 1.3 with Short Header and 6LoWPAN-GHC
This section analyzes the overhead of DTLS 1.3 with short header
[I-D.ietf-tls-dtls13] when compressed with 6LoWPAN-GHC [RFC7400]
[OlegHahm-ghc].
Compressed DTLS 1.3 record layer (18 bytes, 12 bytes overhead):
11 30 05 ae a0 15 56 67 92 ec 4d ff 8a 24 e4 cb
35 b9
Compressed DTLS 1.3 short header (including sequence number):
11 30 05
Ciphertext (including encrypted content type):
ae a0 15 56 67 92 ec
ICV:
4d ff 8a 24 e4 cb 35 b9
Compressed DTLS 1.3 with short header gives 12 bytes overhead.
2.3. TLS 1.2 2.3. TLS 1.2
2.3.1. TLS 1.2 2.3.1. TLS 1.2
This section analyzes the overhead of TLS 1.2 [RFC5246]. The changes This section analyzes the overhead of TLS 1.2 [RFC5246]. The changes
compared to DTLS 1.2 is that the TLS 1.2 record layer does not have compared to DTLS 1.2 is that the TLS 1.2 record layer does not have
epoch and sequence number, and that the version is different. epoch and sequence number, and that the version is different.
TLS 1.2 Record Layer (27 bytes, 21 bytes overhead): TLS 1.2 Record Layer (27 bytes, 21 bytes overhead):
17 03 03 00 16 00 00 00 00 00 00 00 05 ae a0 15 17 03 03 00 16 00 00 00 00 00 00 00 05 ae a0 15
skipping to change at page 13, line 8 skipping to change at page 12, line 8
Connection IDs with the same length. Connection IDs with the same length.
The OSCORE overhead is dependent on the included CoAP Option numbers The OSCORE overhead is dependent on the included CoAP Option numbers
as well as the length of the OSCORE parameters Sender ID and sequence as well as the length of the OSCORE parameters Sender ID and sequence
number. The following overheads apply for all sequence numbers and number. The following overheads apply for all sequence numbers and
Sender IDs with the same length. Sender IDs with the same length.
Sequence Number '05' '1005' '100005' Sequence Number '05' '1005' '100005'
------------------------------------------------------------- -------------------------------------------------------------
DTLS 1.2 29 29 29 DTLS 1.2 29 29 29
DTLS 1.3 16 16 16 DTLS 1.3 11 12 12
DTLS 1.3 (short header) 11 11 11
------------------------------------------------------------- -------------------------------------------------------------
DTLS 1.2 (GHC) 16 16 16 DTLS 1.2 (GHC) 16 16 16
DTLS 1.3 (GHC) 17 17 17 DTLS 1.3 (GHC) 12 13 13
DTLS 1.3 (short header) (GCH) 12 12 12
------------------------------------------------------------- -------------------------------------------------------------
TLS 1.2 21 21 21 TLS 1.2 21 21 21
TLS 1.3 14 14 14 TLS 1.3 14 14 14
------------------------------------------------------------- -------------------------------------------------------------
TLS 1.2 (GHC) 17 18 19 TLS 1.2 (GHC) 17 18 19
TLS 1.3 (GHC) 15 16 17 TLS 1.3 (GHC) 15 16 17
------------------------------------------------------------- -------------------------------------------------------------
OSCORE request 13 14 15 OSCORE request 13 14 15
OSCORE response 11 11 11 OSCORE response 11 11 11
Figure 1: Overhead in bytes as a function of sequence number Figure 1: Overhead in bytes as a function of sequence number
(Connection/Sender ID = '') (Connection/Sender ID = '')
Connection/Sender ID '' '42' '4002' Connection/Sender ID '' '42' '4002'
------------------------------------------------------------- -------------------------------------------------------------
DTLS 1.2 29 30 31 DTLS 1.2 29 30 31
DTLS 1.3 16 17 18 DTLS 1.3 11 12 13
DTLS 1.3 (short header) 11 12 13
------------------------------------------------------------- -------------------------------------------------------------
DTLS 1.2 (GHC) 16 17 18 DTLS 1.2 (GHC) 16 17 18
DTLS 1.3 (GHC) 17 18 19 DTLS 1.3 (GHC) 12 13 14
DTLS 1.3 (short header) (GCH) 12 13 14
------------------------------------------------------------- -------------------------------------------------------------
OSCORE request 13 14 15 OSCORE request 13 14 15
OSCORE response 11 11 11 OSCORE response 11 11 11
Figure 2: Overhead in bytes as a function of Connection/Sender ID Figure 2: Overhead in bytes as a function of Connection/Sender ID
(Sequence Number = '05') (Sequence Number = '05')
Protocol Overhead Overhead (GHC) Protocol Overhead Overhead (GHC)
------------------------------------------------------------- -------------------------------------------------------------
DTLS 1.2 21 8 DTLS 1.2 21 8
DTLS 1.3 8 9 DTLS 1.3 3 4
DTLS 1.3 (short header) 3 4
------------------------------------------------------------- -------------------------------------------------------------
TLS 1.2 13 9 TLS 1.2 13 9
TLS 1.3 6 7 TLS 1.3 6 7
------------------------------------------------------------- -------------------------------------------------------------
OSCORE request 5 OSCORE request 5
OSCORE response 3 OSCORE response 3
Figure 3: Overhead (excluding ICV) in bytes Figure 3: Overhead (excluding ICV) in bytes
(Connection/Sender ID = '', Sequence Number = '05') (Connection/Sender ID = '', Sequence Number = '05')
4. Summary 4. Summary
DTLS 1.2 has quite a large overhead as it uses an explicit sequence DTLS 1.2 has quite a large overhead as it uses an explicit sequence
number and an explicit nonce. TLS 1.2 has significantly less (but number and an explicit nonce. TLS 1.2 has significantly less (but
not small) overhead. TLS 1.3 and DTLS 1.3 have quite small overhead. not small) overhead. TLS 1.3 has quite a small overhead. OSCORE and
OSCORE and DTLS 1.3 with short header format has very small overhead. DTLS 1.3 (using the minimal structure) format have very small
overhead.
The Generic Header Compression (6LoWPAN-GHC) can in addition to DTLS The Generic Header Compression (6LoWPAN-GHC) can in addition to DTLS
1.2 handle TLS 1.2, and DTLS 1.2 with Connection ID. The Generic 1.2 handle TLS 1.2, and DTLS 1.2 with Connection ID. The Generic
Header Compression (6LoWPAN-GHC) works very well for Connection ID Header Compression (6LoWPAN-GHC) works very well for Connection ID
and the overhead seems to increase exactly with the length of the and the overhead seems to increase exactly with the length of the
Connection ID (which is optimal). The compression of TLS 1.2 is not Connection ID (which is optimal). The compression of TLS 1.2 is not
as good as the compression of DTLS 1.2 (as the static dictionary only as good as the compression of DTLS 1.2 (as the static dictionary only
contains the DTLS 1.2 version number). Similar compression levels as contains the DTLS 1.2 version number). Similar compression levels as
for DTLS could be achieved also for TLS 1.2, but this would require for DTLS could be achieved also for TLS 1.2, but this would require
different static dictionaries. For TLS 1.3 and DTLS 1.3, GHC different static dictionaries. For TLS 1.3 and DTLS 1.3, GHC
increases the overhead. The 6LoWPAN-GHC header compression is not increases the overhead. The 6LoWPAN-GHC header compression is not
available when (D)TLS is used over transports that do not use 6LoWPAN available when (D)TLS is used over transports that do not use 6LoWPAN
together with 6LoWPAN-GHC. together with 6LoWPAN-GHC.
The short header format for DTLS 1.3 reduces the header of 5 bytes, Only the minimal header format for DTLS 1.3 was considered, which
by omitting the length value and sending 1 lower bit of epoch value reduces the header of 3 bytes compared to the full header, by
instead of 2, and 12 lower bits of sequence number instead of 30. omitting the 2-byte-long length value and sending 1 byte of sequence
This may create problems reconstructing the full sequence number, if number instead of 2. This may create problems reconstructing the
~2000 datagrams in sequence are lost. full sequence number, if ~2000 datagrams in sequence are lost.
OSCORE has much lower overhead than DTLS 1.2 and TLS 1.2. The OSCORE has much lower overhead than DTLS 1.2 and TLS 1.2. The
overhead of OSCORE is smaller than DTLS 1.2 and TLS 1.2 over 6LoWPAN overhead of OSCORE is smaller than DTLS 1.2 and TLS 1.2 over 6LoWPAN
with compression, and this small overhead is achieved even on with compression, and this small overhead is achieved even on
deployments without 6LoWPAN or 6LoWPAN without DTLS compression. deployments without 6LoWPAN or 6LoWPAN without DTLS compression.
OSCORE is lightweight because it makes use of some excellent features OSCORE is lightweight because it makes use of CoAP, CBOR, and COSE,
in CoAP, CBOR, and COSE. which were designed to have as low overhead as possible.
5. Security Considerations 5. Security Considerations
This document is purely informational. This document is purely informational.
6. IANA Considerations 6. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
7. Informative References 7. Informative References
[I-D.ietf-core-object-security] [I-D.ietf-core-object-security]
Selander, G., Mattsson, J., Palombini, F., and L. Seitz, Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments "Object Security for Constrained RESTful Environments
(OSCORE)", draft-ietf-core-object-security-13 (work in (OSCORE)", draft-ietf-core-object-security-15 (work in
progress), June 2018. progress), August 2018.
[I-D.ietf-tls-dtls-connection-id] [I-D.ietf-tls-dtls-connection-id]
Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom, Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom,
"The Datagram Transport Layer Security (DTLS) Connection "Connection Identifiers for DTLS 1.2", draft-ietf-tls-
Identifier", draft-ietf-tls-dtls-connection-id-00 (work in dtls-connection-id-02 (work in progress), October 2018.
progress), December 2017.
[I-D.ietf-tls-dtls13] [I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-26 (work in progress), March 1.3", draft-ietf-tls-dtls13-30 (work in progress),
2018. November 2018.
[I-D.ietf-tls-tls13] [I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-28 (work in progress), Version 1.3", draft-ietf-tls-tls13-28 (work in progress),
March 2018. March 2018.
[OlegHahm-ghc] [OlegHahm-ghc]
Hahm, O., "Generic Header Compression", July 2016, Hahm, O., "Generic Header Compression", July 2016,
<https://github.com/OlegHahm/ghc>. <https://github.com/OlegHahm/ghc>.
 End of changes. 38 change blocks. 
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