ECDHE_PSK with AES-GCM and AES-CCM Cipher
Suites for Transport Layer Security (TLS) Protocol version 1.2 Ericsson ABSE-164 80 StockholmSweden +46 76 115 35 01john.mattsson@ericsson.com Ericsson 8400 boulevard Decarie Montreal, QC H4P 2N2 Canada +1 514-452-2160 daniel.migault@ericsson.comThis document defines several new cipher suites for the Transport
Layer Security (TLS) protocol version 1.2. The cipher suites are all
based on the Ephemeral Elliptic Curve Diffie-Hellman with Pre-Shared Key
(ECDHE_PSK) key exchange together with the Authenticated Encryption with
Associated Data (AEAD) algorithms AES-GCM and AES-CCM. PSK provides
light and efficient authentication, ECDHE provides forward secrecy, and
AES-GCM and AES-CCM provides encryption and integrity protection. 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 .This document defines new cipher suites that provide Pre-Shared Key
(PSK) authentication, Perfect Forward Secrecy (PFS), and Authenticated
Encryption with Associated Data (AEAD). The cipher suites are defined
for version 1.2 of the Transport Layer Security (TLS) protocol and version 1.2 of the Datagram
Transport Layer Security (DTLS) protocol .Pre-Shared Key (PSK) Authentication is widely used in many scenarios.
One deployment is 3GPP networks where pre-shared keys are used to
authenticate both subscriber and network. Another deployment is
Internet of Things where PSK authentication is often preferred for
performance and energy efficiency reasons. In both scenarios the
endpoints are owned/controlled by a party that provisions the pre-shared
keys and makes sure that they provide a high level of entropy.Perfect Forward Secrecy (PFS) is a strongly recommended feature in
security protocol design and can be accomplished by using an ephemeral
Diffie-Hellman key exchange method. Ephemeral Elliptic Curve
Diffie-Hellman (ECDHE) provides PFS with excellent performance and small
key sizes. ECDHE is mandatory to implement in both HTTP/2 and CoAP .AEAD algorithms that combine encryption and integrity protection are
strongly recommended for (D)TLS and non-AEAD algorithms
are forbidden to use in TLS 1.3 . The
AEAD algorithms considered in this document are AES-GCM and AES-CCM. The
use of AES-GCM in TLS is defined in and the
use of AES-CCM is defined in . defines Pre-Shared Key (PSK) cipher suites
for TLS but does not consider Elliptic Curve Cryptography. introduces Elliptic Curve Cryptography for TLS but
does not consider PSK authentication. describes
the use of AES-GCM in combination with PSK authentication, but does not
consider ECDHE. describes the use of PSK in
combination with ECDHE but does not consider AES-GCM or AES-CCM.The cipher suites defined in this document are based on the AES-GCM
and AES-CCM Authenticated Encryption with Associated Data (AEAD)
algorithms AEAD_AES_128_GCM, AEAD_AES_256_GCM, AEAD_AES_128_CCM_8
defined in and AEAD_AES_128_CCM defined in
.Messages and premaster secret construction in this document are
defined in . The ServerKeyExchange and
ClientKeyExchange messages are used and the premaster secret is computed
as for the ECDHE_PSK key exchange. The elliptic curve parameters used in
in the Diffie-Hellman parameters are negotiated using extensions defined
in .For TLS 1.2, the following cipher suites are defined:The assigned code points can only be used for TLS 1.2. The cipher suites defined in this document MUST NOT be negotiated for any version of (D)TLS other than TLS 1.2. Servers MUST NOT select one of these cipher suites when selecting TLS version other than TLS 1.2. A client MUST treat the selection of these cipher suites in combination with a different version of TLS as an error and generate a fatal 'illegal_parameter' TLS alert.Cipher suites TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384, TLS_AES_128_CCM_8_SHA256 and TLS_AES_128_CCM_SHA256 are used to support equivalent functionality in TLS 1.3 .This document defines the following new cipher suites, whose values
have been assigned in the TLS Cipher Suite Registry defined by .NOTE TO THE RFC EDITOR: PLEASE REMOVE THIS PARAGRAPH. The cipher suite numbers listed in the last column are numbers used
for cipher suite interoperability testing and it's suggested that IANA
use these values for assignment.The security considerations in TLS 1.2 , DTLS
1.2 , PSK Ciphersuites for TLS , ECDHE_PSK ,
AES-GCM , and AES-CCM
apply to this document as well.All the cipher suites defined in this document provide
confidentiality, mutual authentication, and forward secrecy. The
AES-128 cipher suites provide 128-bit security and the AES-256 cipher
suites provide at least 192-bit security. However, AES_128_CCM_8 only
provides 64-bit security against message forgery.The Pre-Shared Keys used for authentication MUST have a security level equal
or higher than the cipher suite used, i.e., at least 128-bit for the AES-128
cipher suites and at least 192-bit for the AES-256 cipher suites.GCM or CCM encryption - even of different clear text - re-using a
nonce with a same key undermines the security of GCM and CCM. As a
result, GCM and CCM MUST only be used with a system guaranteeing nonce
uniqueness .The authors would like to thank Ilari Liusvaara, Eric Rescorla, Dan
Harkins, Russ Housley, Dan Harkins, Martin Thomson, Nikos
Mavrogiannopoulos, Peter Dettman, Xiaoyin Liu, Joseph Salowey, Sean
Turner Dave Garrett, Martin Rex and Kathleen Moriarty for their
valuable comments and feedback.