draft-ietf-tls-psk-08.txt		draft-ietf-tls-psk-09.txt
	TLS Working Group P. Eronen, Ed.		TLS Working Group P. Eronen, Ed.
	Internet-Draft Nokia		Internet-Draft Nokia
	Expires: October 25, 2005 H. Tschofenig, Ed.		Expires: December 20, 2005 H. Tschofenig, Ed.
	Siemens		Siemens
	April 26, 2005		June 21, 2005
	Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)		Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)
	draft-ietf-tls-psk-08.txt		draft-ietf-tls-psk-09.txt
	Status of this Memo		Status of this Memo
	By submitting this Internet-Draft, each author represents that any		By submitting this Internet-Draft, each author represents that any
	applicable patent or other IPR claims of which he or she is aware		applicable patent or other IPR claims of which he or she is aware
	have been or will be disclosed, and any of which he or she becomes		have been or will be disclosed, and any of which he or she becomes
	aware will be disclosed, in accordance with Section 6 of BCP 79.		aware will be disclosed, in accordance with Section 6 of BCP 79.
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	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF), its areas, and its working groups. Note that
	skipping to change at page 1, line 35		skipping to change at page 1, line 35
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
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	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.		http://www.ietf.org/ietf/1id-abstracts.txt.
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	This Internet-Draft will expire on October 25, 2005.		This Internet-Draft will expire on December 20, 2005.
	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2005).		Copyright (C) The Internet Society (2005).
	Abstract		Abstract
	This document specifies three sets of new ciphersuites for the		This document specifies three sets of new ciphersuites for the
	Transport Layer Security (TLS) protocol to support authentication		Transport Layer Security (TLS) protocol to support authentication
	based on pre-shared keys. These pre-shared keys are symmetric keys,		based on pre-shared keys. These pre-shared keys are symmetric keys,
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	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.1 Applicability statement . . . . . . . . . . . . . . . . . 4		1.1 Applicability statement . . . . . . . . . . . . . . . . . 4
	1.2 Conventions used in this document . . . . . . . . . . . . 4		1.2 Conventions used in this document . . . . . . . . . . . . 4
	2. PSK key exchange algorithm . . . . . . . . . . . . . . . . . . 5		2. PSK key exchange algorithm . . . . . . . . . . . . . . . . . . 5
	3. DHE_PSK key exchange algorithm . . . . . . . . . . . . . . . . 7		3. DHE_PSK key exchange algorithm . . . . . . . . . . . . . . . . 7
	4. RSA_PSK key exchange algorithm . . . . . . . . . . . . . . . . 8		4. RSA_PSK key exchange algorithm . . . . . . . . . . . . . . . . 8
	5. Conformance requirements . . . . . . . . . . . . . . . . . . . 9		5. Conformance requirements . . . . . . . . . . . . . . . . . . . 9
	5.1 PSK identity encoding . . . . . . . . . . . . . . . . . . 9		5.1 PSK identity encoding . . . . . . . . . . . . . . . . . . 9
	5.2 Identity hint . . . . . . . . . . . . . . . . . . . . . . 9		5.2 Identity hint . . . . . . . . . . . . . . . . . . . . . . 10
	5.3 Requirements for TLS implementations . . . . . . . . . . 10		5.3 Requirements for TLS implementations . . . . . . . . . . 10
	5.4 Requirements for management interfaces . . . . . . . . . 10		5.4 Requirements for management interfaces . . . . . . . . . 10
	6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 11		6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 11
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 11		7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
	7.1 Perfect forward secrecy (PFS) . . . . . . . . . . . . . . 11		7.1 Perfect forward secrecy (PFS) . . . . . . . . . . . . . . 11
	7.2 Brute-force and dictionary attacks . . . . . . . . . . . 11		7.2 Brute-force and dictionary attacks . . . . . . . . . . . 11
	7.3 Identity privacy . . . . . . . . . . . . . . . . . . . . 12		7.3 Identity privacy . . . . . . . . . . . . . . . . . . . . 12
	7.4 Implementation notes . . . . . . . . . . . . . . . . . . 12		7.4 Implementation notes . . . . . . . . . . . . . . . . . . 12
	8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12		8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13		9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
	9.1 Normative References . . . . . . . . . . . . . . . . . . 13		9.1 Normative References . . . . . . . . . . . . . . . . . . 13
	9.2 Informative References . . . . . . . . . . . . . . . . . 13		9.2 Informative References . . . . . . . . . . . . . . . . . 13
	Authors' and Contributors' Addresses . . . . . . . . . . . . . . . 15		Authors' and Contributors' Addresses . . . . . . . . . . . . . . . 15
	Appendix A. Changelog . . . . . . . . . . . . . . . . . . . . . . 16		Appendix A. Changelog . . . . . . . . . . . . . . . . . . . . . . 16
	1. Introduction		1. Introduction
	Usually TLS uses public key certificates [3] or Kerberos [12] for		Usually TLS uses public key certificates [TLS] or Kerberos [KERB] for
	authentication. This document describes how to use symmetric keys		authentication. This document describes how to use symmetric keys
	(later called pre-shared keys or PSKs), shared in advance among the		(later called pre-shared keys or PSKs), shared in advance among the
	communicating parties, to establish a TLS connection.		communicating parties, to establish a TLS connection.
	There are basically two reasons why one might want to do this:		There are basically two reasons why one might want to do this:
	o First, using pre-shared keys can, depending on the ciphersuite,		o First, using pre-shared keys can, depending on the ciphersuite,
	avoid the need for public key operations. This is useful if TLS		avoid the need for public key operations. This is useful if TLS
	is used in performance-constrained environments with limited CPU		is used in performance-constrained environments with limited CPU
	power.		power.
	skipping to change at page 3, line 29		skipping to change at page 3, line 29
	o Second, pre-shared keys may be more convenient from a key		o Second, pre-shared keys may be more convenient from a key
	management point of view. For instance, in closed environments		management point of view. For instance, in closed environments
	where the connections are mostly configured manually in advance,		where the connections are mostly configured manually in advance,
	it may be easier to configure a PSK than to use certificates.		it may be easier to configure a PSK than to use certificates.
	Another case is when the parties already have a mechanism for		Another case is when the parties already have a mechanism for
	setting up a shared secret key, and that mechanism could be used		setting up a shared secret key, and that mechanism could be used
	to "bootstrap" a key for authenticating a TLS connection.		to "bootstrap" a key for authenticating a TLS connection.
	This document specifies three sets of new ciphersuites for TLS.		This document specifies three sets of new ciphersuites for TLS.
	These ciphersuites use new key exchange algorithms, and re-use		These ciphersuites use new key exchange algorithms, and re-use
	existing cipher and MAC algorithms from [3] and [2]. A summary of		existing cipher and MAC algorithms from [TLS] and [AES]. A summary
	these ciphersuites is shown below.		of these ciphersuites is shown below.
	CipherSuite Key Exchange Cipher Hash		CipherSuite Key Exchange Cipher Hash
	TLS_PSK_WITH_RC4_128_SHA PSK RC4_128 SHA		TLS_PSK_WITH_RC4_128_SHA PSK RC4_128 SHA
	TLS_PSK_WITH_3DES_EDE_CBC_SHA PSK 3DES_EDE_CBC SHA		TLS_PSK_WITH_3DES_EDE_CBC_SHA PSK 3DES_EDE_CBC SHA
	TLS_PSK_WITH_AES_128_CBC_SHA PSK AES_128_CBC SHA		TLS_PSK_WITH_AES_128_CBC_SHA PSK AES_128_CBC SHA
	TLS_PSK_WITH_AES_256_CBC_SHA PSK AES_256_CBC SHA		TLS_PSK_WITH_AES_256_CBC_SHA PSK AES_256_CBC SHA
	TLS_DHE_PSK_WITH_RC4_128_SHA DHE_PSK RC4_128 SHA		TLS_DHE_PSK_WITH_RC4_128_SHA DHE_PSK RC4_128 SHA
	TLS_DHE_PSK_WITH_3DES_EDE_CBC_SHA DHE_PSK 3DES_EDE_CBC SHA		TLS_DHE_PSK_WITH_3DES_EDE_CBC_SHA DHE_PSK 3DES_EDE_CBC SHA
	TLS_DHE_PSK_WITH_AES_128_CBC_SHA DHE_PSK AES_128_CBC SHA		TLS_DHE_PSK_WITH_AES_128_CBC_SHA DHE_PSK AES_128_CBC SHA
	skipping to change at page 4, line 28		skipping to change at page 4, line 28
	alternatives may be more appropriate.		alternatives may be more appropriate.
	If the main goal is to avoid PKIs, another possibility worth		If the main goal is to avoid PKIs, another possibility worth
	considering is to use self-signed certificates with public key		considering is to use self-signed certificates with public key
	fingerprints. Instead of manually configuring a shared secret in,		fingerprints. Instead of manually configuring a shared secret in,
	for instance, some configuration file, a fingerprint (hash) of the		for instance, some configuration file, a fingerprint (hash) of the
	other party's public key (or certificate) could be placed there		other party's public key (or certificate) could be placed there
	instead.		instead.
	It is also possible to use the SRP (Secure Remote Password)		It is also possible to use the SRP (Secure Remote Password)
	ciphersuites for shared secret authentication [14]. SRP was designed		ciphersuites for shared secret authentication [SRP]. SRP was
	to be used with passwords, and incorporates protection against		designed to be used with passwords, and incorporates protection
	dictionary attacks. However, it is computationally more expensive		against dictionary attacks. However, it is computationally more
	than the PSK ciphersuites in Section 2.		expensive than the PSK ciphersuites in Section 2.
	1.2 Conventions used in this document		1.2 Conventions used in this document
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [1].		document are to be interpreted as described in [KEYWORDS].
	2. PSK key exchange algorithm		2. PSK key exchange algorithm
	This section defines the PSK key exchange algorithm and associated		This section defines the PSK key exchange algorithm and associated
	ciphersuites. These ciphersuites use only symmetric key algorithms.		ciphersuites. These ciphersuites use only symmetric key algorithms.
	It is assumed that the reader is familiar with ordinary TLS		It is assumed that the reader is familiar with ordinary TLS
	handshake, shown below. The elements in parenthesis are not included		handshake, shown below. The elements in parenthesis are not included
	when PSK key exchange algorithm is used, and "*" indicates a		when PSK key exchange algorithm is used, and "*" indicates a
	situation-dependent message that is not always sent.		situation-dependent message that is not always sent.
	skipping to change at page 5, line 44		skipping to change at page 5, line 44
	authentication by including one or more PSK ciphersuites in the		authentication by including one or more PSK ciphersuites in the
	ClientHello message. If the TLS server also wants to use pre-shared		ClientHello message. If the TLS server also wants to use pre-shared
	keys, it selects one of the PSK ciphersuites, places the selected		keys, it selects one of the PSK ciphersuites, places the selected
	ciphersuite in the ServerHello message, and includes an appropriate		ciphersuite in the ServerHello message, and includes an appropriate
	ServerKeyExchange message (see below). The Certificate and		ServerKeyExchange message (see below). The Certificate and
	CertificateRequest payloads are omitted from the response.		CertificateRequest payloads are omitted from the response.
	Both clients and servers may have pre-shared keys with several		Both clients and servers may have pre-shared keys with several
	different parties. The client indicates which key to use by		different parties. The client indicates which key to use by
	including a "PSK identity" in the ClientKeyExchange message (note		including a "PSK identity" in the ClientKeyExchange message (note
	that unlike in [7], the session_id field in ClientHello message keeps		that unlike in [SHAREDKEYS], the session_id field in ClientHello
	its usual meaning). To help the client in selecting which identity		message keeps its usual meaning). To help the client in selecting
	to use, the server can provide a "PSK identity hint" in the		which identity to use, the server can provide a "PSK identity hint"
	ServerKeyExchange message. If no hint is provided, the		in the ServerKeyExchange message. If no hint is provided, the
	ServerKeyExchange message is omitted. See Section 5 for more		ServerKeyExchange message is omitted. See Section 5 for more
	detailed description of these fields.		detailed description of these fields.
	The format of the ServerKeyExchange and ClientKeyExchange messages is		The format of the ServerKeyExchange and ClientKeyExchange messages is
	shown below.		shown below.
	struct {		struct {
	select (KeyExchangeAlgorithm) {		select (KeyExchangeAlgorithm) {
	/* other cases for rsa, diffie_hellman, etc. */		/* other cases for rsa, diffie_hellman, etc. */
	case psk: /* NEW */		case psk: /* NEW */
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	Here "other_secret" is either zeroes (plain PSK case), or comes		Here "other_secret" is either zeroes (plain PSK case), or comes
	from the Diffie-Hellman or RSA exchange (DHE_PSK and RSA_PSK,		from the Diffie-Hellman or RSA exchange (DHE_PSK and RSA_PSK,
	respectively). See Sections 3 and 4 for a more detailed		respectively). See Sections 3 and 4 for a more detailed
	description.		description.
	Note 2: Using zeroes for "other_secret" effectively means that		Note 2: Using zeroes for "other_secret" effectively means that
	only the HMAC-SHA1 part (but not the HMAC-MD5 part) of the TLS PRF		only the HMAC-SHA1 part (but not the HMAC-MD5 part) of the TLS PRF
	is used when constructing the master secret. This was considered		is used when constructing the master secret. This was considered
	more elegant from an analytical viewpoint than, for instance,		more elegant from an analytical viewpoint than, for instance,
	using the same key for both the HMAC-MD5 and HMAC-SHA1 parts. See		using the same key for both the HMAC-MD5 and HMAC-SHA1 parts. See
	[8] for a more detailed rationale.		[KRAWCZYK] for a more detailed rationale.
	The TLS handshake is authenticated using the Finished messages as		The TLS handshake is authenticated using the Finished messages as
	usual.		usual.
	If the server does not recognize the PSK identity, it MAY respond		If the server does not recognize the PSK identity, it MAY respond
	with an "unknown_psk_identity" alert message. Alternatively, if the		with an "unknown_psk_identity" alert message. Alternatively, if the
	server wishes to hide the fact that the PSK identity was not known,		server wishes to hide the fact that the PSK identity was not known,
	it MAY continue the protocol as if the PSK identity existed but the		it MAY continue the protocol as if the PSK identity existed but the
	key was incorrect: that is, respond with a "decrypt_error" alert.		key was incorrect: that is, respond with a "decrypt_error" alert.
	skipping to change at page 7, line 42		skipping to change at page 7, line 42
	select (KeyExchangeAlgorithm) {		select (KeyExchangeAlgorithm) {
	/* other cases for rsa, diffie_hellman, etc. */		/* other cases for rsa, diffie_hellman, etc. */
	case diffie_hellman_psk: /* NEW */		case diffie_hellman_psk: /* NEW */
	opaque psk_identity<0..2^16-1>;		opaque psk_identity<0..2^16-1>;
	ClientDiffieHellmanPublic public;		ClientDiffieHellmanPublic public;
	} exchange_keys;		} exchange_keys;
	} ClientKeyExchange;		} ClientKeyExchange;
	The premaster secret is formed as follows. First, perform the		The premaster secret is formed as follows. First, perform the
	Diffie-Hellman computation in the same way as for other		Diffie-Hellman computation in the same way as for other
	Diffie-Hellman based ciphersuites in [3]. Let Z be the value		Diffie-Hellman based ciphersuites in [TLS]. Let Z be the value
	produced by this computation (with leading zero bytes stripped as in		produced by this computation (with leading zero bytes stripped as in
	other Diffie-Hellman based ciphersuites). Concatenate a uint16		other Diffie-Hellman based ciphersuites). Concatenate a uint16
	containing the length of Z (in octets), Z itself, a uint16 containing		containing the length of Z (in octets), Z itself, a uint16 containing
	the length of the PSK (in octets), and the PSK itself.		the length of the PSK (in octets), and the PSK itself.
	This corresponds to the general structure for the premaster secrets		This corresponds to the general structure for the premaster secrets
	(see Note 1 in Section 2) in this document, with "other_secret"		(see Note 1 in Section 2) in this document, with "other_secret"
	containing Z.		containing Z.
	4. RSA_PSK key exchange algorithm		4. RSA_PSK key exchange algorithm
	skipping to change at page 8, line 35		skipping to change at page 8, line 35
	/* other cases for rsa, diffie_hellman, etc. */		/* other cases for rsa, diffie_hellman, etc. */
	case rsa_psk: /* NEW */		case rsa_psk: /* NEW */
	opaque psk_identity<0..2^16-1>;		opaque psk_identity<0..2^16-1>;
	EncryptedPreMasterSecret;		EncryptedPreMasterSecret;
	} exchange_keys;		} exchange_keys;
	} ClientKeyExchange;		} ClientKeyExchange;
	The EncryptedPreMasterSecret field sent from the client to the server		The EncryptedPreMasterSecret field sent from the client to the server
	contains a 2-byte version number and a 46-byte random value,		contains a 2-byte version number and a 46-byte random value,
	encrypted using the server's RSA public key as described in Section		encrypted using the server's RSA public key as described in Section
	7.4.7.1 of [3]. The actual premaster secret is formed by both		7.4.7.1 of [TLS]. The actual premaster secret is formed by both
	parties as follows: concatenate a uint16 with the value 48, the		parties as follows: concatenate a uint16 with the value 48, the
	2-byte version number and the 46-byte random value, a uint16		2-byte version number and the 46-byte random value, a uint16
	containing the length of the PSK (in octets), and the PSK itself.		containing the length of the PSK (in octets), and the PSK itself.
	(The premaster secret is thus 52 octets longer than the PSK.)		(The premaster secret is thus 52 octets longer than the PSK.)
	This corresponds to the general structure for the premaster secrets		This corresponds to the general structure for the premaster secrets
	(see Note 1 in Section 2) in this document, with "other_secret"		(see Note 1 in Section 2) in this document, with "other_secret"
	containing both the 2-byte version number and the 46-byte random		containing both the 2-byte version number and the 46-byte random
	value.		value.
	skipping to change at page 9, line 25		skipping to change at page 9, line 25
	protocol, and what kinds of identities and keys implementations have		protocol, and what kinds of identities and keys implementations have
	to support.		to support.
	The requirements for implementations are divided to two categories,		The requirements for implementations are divided to two categories,
	requirements for TLS implementations and management interfaces. In		requirements for TLS implementations and management interfaces. In
	this context, "TLS implementation" refers to a TLS library or module		this context, "TLS implementation" refers to a TLS library or module
	that is intended to be used for several different purposes, while		that is intended to be used for several different purposes, while
	"management interface" would typically be implemented by a particular		"management interface" would typically be implemented by a particular
	application that uses TLS.		application that uses TLS.
			This document does not specify how the server stores the keys and
			identities, or how exactly it finds the key corresponding to the
			identity it receives. For instance, if the identity is a domain
			name, it might be appropriate to do a case-insensitive lookup. It is
			RECOMMENDED that before looking up the key, the server processes the
			PSK identity with a stringprep profile [STRINGPREP] appropriate for
			the identity in question (such as Nameprep [NAMEPREP] for components
			of domain names or SASLprep for usernames [SASLPREP]).
	5.1 PSK identity encoding		5.1 PSK identity encoding
	The PSK identity MUST be first converted to a character string, and		The PSK identity MUST be first converted to a character string, and
	then encoded to octets using UTF-8 [5]. For instance,		then encoded to octets using UTF-8 [UTF8]. For instance,
	o IPv4 addresses are sent as dotted-decimal strings (e.g.,		o IPv4 addresses are sent as dotted-decimal strings (e.g.,
	"192.0.1.2"), not as 32-bit integers in network byte order.		"192.0.2.1"), not as 32-bit integers in network byte order.
	o Domain names are sent in their usual text form (e.g.,		o Domain names are sent in their usual text form (e.g.,
	"www.example.com" or "embedded.dot.example.net"), not in DNS		"www.example.com" or "embedded.dot.example.net"), not in DNS
	protocol format.		protocol format.
	o X.500 Distinguished Names are sent in their string representation		o X.500 Distinguished Names are sent in their string representation
	[9], not as BER-encoded ASN.1.		[LDAPDN], not as BER-encoded ASN.1.
	This encoding is clearly not optimal for many types of identities.		This encoding is clearly not optimal for many types of identities.
	It was chosen to avoid identity type specific parsing and encoding		It was chosen to avoid identity type specific parsing and encoding
	code in implementations where the identity is configured by a person		code in implementations where the identity is configured by a person
	using some kind of management interface. Requiring such identity		using some kind of management interface. Requiring such identity
	type specific code would also increase the chances for		type specific code would also increase the chances for
	interoperability problems resulting from different implementations		interoperability problems resulting from different implementations
	supporting different identity types.		supporting different identity types.
	5.2 Identity hint		5.2 Identity hint
	skipping to change at page 10, line 22		skipping to change at page 10, line 31
	keys is RECOMMENDED.		keys is RECOMMENDED.
	5.4 Requirements for management interfaces		5.4 Requirements for management interfaces
	In the absence of an application profile specification specifying		In the absence of an application profile specification specifying
	otherwise, a management interface for entering the PSK and/or PSK		otherwise, a management interface for entering the PSK and/or PSK
	identity MUST support the following:		identity MUST support the following:
	o Entering PSK identities consisting of up to 128 printable Unicode		o Entering PSK identities consisting of up to 128 printable Unicode
	characters. Supporting as wide character repertoire and as long		characters. Supporting as wide character repertoire and as long
	identities as feasible is RECOMMENDED, as is processing the		identities as feasible is RECOMMENDED.
	character string with an appropriate stringprep [10] profile.
	o Entering PSKs up to 64 octets in length as ASCII strings and in		o Entering PSKs up to 64 octets in length as ASCII strings and in
	hexadecimal encoding.		hexadecimal encoding.
	6. IANA considerations		6. IANA considerations
	IANA does not currently have a registry for TLS-related numbers, so		IANA does not currently have a registry for TLS ciphersuite or alert
	there are no IANA actions associated with this document.		numbers, so there are no IANA actions associated with this document.
	For easier reference in the future, the ciphersuite numbers defined		For easier reference in the future, the ciphersuite numbers defined
	in this document are summarized below.		in this document are summarized below.
	CipherSuite TLS_PSK_WITH_RC4_128_SHA = { 0x00, 0x8A };		CipherSuite TLS_PSK_WITH_RC4_128_SHA = { 0x00, 0x8A };
	CipherSuite TLS_PSK_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x8B };		CipherSuite TLS_PSK_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x8B };
	CipherSuite TLS_PSK_WITH_AES_128_CBC_SHA = { 0x00, 0x8C };		CipherSuite TLS_PSK_WITH_AES_128_CBC_SHA = { 0x00, 0x8C };
	CipherSuite TLS_PSK_WITH_AES_256_CBC_SHA = { 0x00, 0x8D };		CipherSuite TLS_PSK_WITH_AES_256_CBC_SHA = { 0x00, 0x8D };
	CipherSuite TLS_DHE_PSK_WITH_RC4_128_SHA = { 0x00, 0x8E };		CipherSuite TLS_DHE_PSK_WITH_RC4_128_SHA = { 0x00, 0x8E };
	CipherSuite TLS_DHE_PSK_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x8F };		CipherSuite TLS_DHE_PSK_WITH_3DES_EDE_CBC_SHA = { 0x00, 0x8F };
	skipping to change at page 12, line 23		skipping to change at page 12, line 23
	For the DHE_PSK ciphersuites, an attacker can obtain the information		For the DHE_PSK ciphersuites, an attacker can obtain the information
	by getting a valid client to attempt connection with the attacker.		by getting a valid client to attempt connection with the attacker.
	Passive eavesdropping alone is not sufficient.		Passive eavesdropping alone is not sufficient.
	For the RSA_PSK ciphersuites, only the server (authenticated using		For the RSA_PSK ciphersuites, only the server (authenticated using
	RSA and certificates) can obtain sufficient information for an		RSA and certificates) can obtain sufficient information for an
	off-line attack.		off-line attack.
	It is RECOMMENDED that implementations that allow the administrator		It is RECOMMENDED that implementations that allow the administrator
	to manually configure the PSK also provide a functionality for		to manually configure the PSK also provide a functionality for
	generating a new random PSK, taking [4] into account.		generating a new random PSK, taking [RANDOMNESS] into account.
	7.3 Identity privacy		7.3 Identity privacy
	The PSK identity is sent in cleartext. While using a user name or		The PSK identity is sent in cleartext. While using a user name or
	other similar string as the PSK identity is the most straightforward		other similar string as the PSK identity is the most straightforward
	option, it may lead to problems in some environments since an		option, it may lead to problems in some environments since an
	eavesdropper is able to identify the communicating parties. Even		eavesdropper is able to identify the communicating parties. Even
	when the identity does not reveal any information itself, reusing the		when the identity does not reveal any information itself, reusing the
	same identity over time may eventually allow an attacker to perform		same identity over time may eventually allow an attacker to perform
	traffic analysis to identify the parties. It should be noted that		traffic analysis to identify the parties. It should be noted that
	this is no worse than client certificates, since they are also sent		this is no worse than client certificates, since they are also sent
	in cleartext.		in cleartext.
	7.4 Implementation notes		7.4 Implementation notes
	The implementation notes in [11] about correct implementation and use		The implementation notes in [TLS11] about correct implementation and
	of RSA (including Section 7.4.7.1) and Diffie-Hellman (including		use of RSA (including Section 7.4.7.1) and Diffie-Hellman (including
	Appendix F.1.1.3) apply to the DHE_PSK and RSA_PSK ciphersuites as		Appendix F.1.1.3) apply to the DHE_PSK and RSA_PSK ciphersuites as
	well.		well.
	8. Acknowledgments		8. Acknowledgments
	The protocol defined in this document is heavily based on work by Tim		The protocol defined in this document is heavily based on work by Tim
	Dierks and Peter Gutmann, and borrows some text from [7] and [2].		Dierks and Peter Gutmann, and borrows some text from [SHAREDKEYS] and
	The DHE_PSK and RSA_PSK ciphersuites are based on earlier work in		[AES]. The DHE_PSK and RSA_PSK ciphersuites are based on earlier
	[6].		work in [KEYEX].
	Valuable feedback was also provided by Bernard Aboba, Lakshminath		Valuable feedback was also provided by Bernard Aboba, Lakshminath
	Dondeti, Philip Ginzboorg, Peter Gutmann, Russ Housley, David Jablon,		Dondeti, Philip Ginzboorg, Peter Gutmann, Sam Hartman, Russ Housley,
	Nikos Mavroyanopoulos, Bodo Moeller, Eric Rescorla, and Mika		David Jablon, Nikos Mavroyanopoulos, Bodo Moeller, Eric Rescorla, and
	Tervonen.		Mika Tervonen.
	When the first version of this draft was almost ready, the authors		When the first version of this draft was almost ready, the authors
	learned that something similar had been proposed already in 1996		learned that something similar had been proposed already in 1996
	[13]. However, this draft is not intended for web password		[PASSAUTH]. However, this draft is not intended for web password
	authentication, but rather for other uses of TLS.		authentication, but rather for other uses of TLS.
	9. References		9. References
	9.1 Normative References		9.1 Normative References
	[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement		[AES] Chown, P., "Advanced Encryption Standard (AES)
	Levels", RFC 2119, March 1997.		Ciphersuites for Transport Layer Security (TLS)", RFC
			3268, June 2002.
	[2] Chown, P., "Advanced Encryption Standard (AES) Ciphersuites		[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
	for Transport Layer Security (TLS)", RFC 3268, June 2002.		Requirement Levels", RFC 2119, March 1997.
	[3] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC		[RANDOMNESS]
	2246, January 1999.		Eastlake, D., 3rd, Schiller, J., and S. Crocker,
			"Randomness Requirements for Security", BCP 106, RFC 4086,
			June 2005.
	[4] Eastlake, D., Crocker, S. and J. Schiller, "Randomness		[TLS] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
	Recommendations for Security", RFC 1750, December 1994.		RFC 2246, January 1999.
	[5] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC		[UTF8] Yergeau, F., "UTF-8, a transformation format of ISO
	3629, November 2003.		10646", RFC 3629, November 2003.
	9.2 Informative References		9.2 Informative References
	[6] Badra, M., Cherkaoui, O., Hajjeh, I. and A. Serhrouchni,		[KERB] Medvinsky, A. and M. Hur, "Addition of Kerberos Cipher
	"Pre-Shared-Key key Exchange methods for TLS",		Suites to Transport Layer Security (TLS)", RFC 2712,
	draft-badra-tls-key-exchange-00 (work in progress), August		October 1999.
	2004.
	[7] Gutmann, P., "Use of Shared Keys in the TLS Protocol",		[KEYEX] Badra, M., Cherkaoui, O., Hajjeh, I. and A. Serhrouchni,
	draft-ietf-tls-sharedkeys-02 (expired), October 2003.		"Pre-Shared-Key key Exchange methods for TLS",
			draft-badra-tls-key-exchange-00 (expired), August 2004.
	[8] Krawczyk, H., "Re: TLS shared keys PRF", message on		[KRAWCZYK] Krawczyk, H., "Re: TLS shared keys PRF", message on
	ietf-tls@lists.certicom.com mailing list 2004-01-13,		ietf-tls@lists.certicom.com mailing list 2004-01-13,
	http://www.imc.org/ietf-tls/mail-archive/msg04098.html.		http://www.imc.org/ietf-tls/mail-archive/msg04098.html.
	[9] Zeilenga, K., "LDAP: String Representation of Distinguished		[LDAPDN] Zeilenga, K., "LDAP: String Representation of
	Names", draft-ietf-ldapbis-dn-15 (work in progress), October		Distinguished Names", draft-ietf-ldapbis-dn-16 (work in
	2004.		progress), February 2005.
	[10] Hoffman, P. and M. Blanchet, "Preparation of Internationalized		[NAMEPREP] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
	Strings ("stringprep")", RFC 3454, December 2002.		Profile for Internationalized Domain Names (IDN)", RFC
			3491, March 2003.
	[11] Dierks, T. and E. Rescorla, "The TLS Protocol Version 1.1",		[PASSAUTH] Simon, D., "Addition of Shared Key Authentication to
	draft-ietf-tls-rfc2246-bis-10 (work in progress), April 2005.		Transport Layer Security (TLS)",
			draft-ietf-tls-passauth-00 (expired), November 1996.
	[12] Medvinsky, A. and M. Hur, "Addition of Kerberos Cipher Suites		[SASLPREP] Zeilenga, K., "SASLprep: Stringprep Profile for User Names
	to Transport Layer Security (TLS)", RFC 2712, October 1999.		and Passwords", RFC 4013, February 2005.
	[13] Simon, D., "Addition of Shared Key Authentication to Transport		[SHAREDKEYS]
	Layer Security (TLS)", draft-ietf-tls-passauth-00 (expired),		Gutmann, P., "Use of Shared Keys in the TLS Protocol",
	November 1996.		draft-ietf-tls-sharedkeys-02 (expired), October 2003.
	[14] Taylor, D., Wu, T., Mavroyanopoulos, N. and T. Perrin, "Using		[SRP] Taylor, D., Wu, T., Mavroyanopoulos, N. and T. Perrin,
	SRP for TLS Authentication", draft-ietf-tls-srp-09 (work in		"Using SRP for TLS Authentication", draft-ietf-tls-srp-09
	progress), March 2005.		(work in progress), March 2005.
			[STRINGPREP]
			Hoffman, P. and M. Blanchet, "Preparation of
			Internationalized Strings ("stringprep")", RFC 3454,
			December 2002.
			[TLS11] Dierks, T. and E. Rescorla, "The TLS Protocol Version
			1.1", draft-ietf-tls-rfc2246-bis-12 (work in progress),
			June 2005.
	Authors' and Contributors' Addresses		Authors' and Contributors' Addresses
	Pasi Eronen		Pasi Eronen
	Nokia Research Center		Nokia Research Center
	P.O. Box 407		P.O. Box 407
	FIN-00045 Nokia Group		FIN-00045 Nokia Group
	Finland		Finland
	Email: pasi.eronen@nokia.com		Email: pasi.eronen@nokia.com
	skipping to change at page 16, line 10		skipping to change at page 16, line 10
	46 rue Barrault		46 rue Barrault
	75634 Paris		75634 Paris
	France		France
	Email: Ahmed.Serhrouchni@enst.fr		Email: Ahmed.Serhrouchni@enst.fr
	Appendix A. Changelog		Appendix A. Changelog
	(This section should be removed by the RFC Editor before		(This section should be removed by the RFC Editor before
	publication.)		publication.)
			Changes from -08 to -09:
			o Clarified internationalization of PSK identities in Section 5.
			o Corrected the example IP address in Section 5.1.
			o Small clarification to IANA considerations on Section 6.
			o Editorial: changed numeric references to symbolic ones, updated
			references to latest versions.
	Changes from -07 to -08:		Changes from -07 to -08:
	o Added table of contents and updated I-D boilerplate.		o Added table of contents and updated I-D boilerplate.
	o Small clarification to motivation in Section 1.		o Small clarification to motivation in Section 1.
	o Small clarification to note 2 in Section 2.		o Small clarification to note 2 in Section 2.
	o Corrected all instances of "an uint16" to "a uint16".		o Corrected all instances of "an uint16" to "a uint16".
	skipping to change at page 16, line 44		skipping to change at page 17, line 6
	o Omit ServerKeyExchange message (in PSK/RSA_PSK versions) if no		o Omit ServerKeyExchange message (in PSK/RSA_PSK versions) if no
	identity hint is provided.		identity hint is provided.
	Changes from -03 to -04:		Changes from -03 to -04:
	o Added a note about premaster secret "general structure" in		o Added a note about premaster secret "general structure" in
	Sections 3 and 4.		Sections 3 and 4.
	o Something in the I-D submission procedure had removed all		o Something in the I-D submission procedure had removed all
	circumflexes from -03 version, turning e.g. "2^16" (two-to-		circumflexes from -03 version, turning e.g. "2^16" (two-to- the
	the sixteenth power) to "216" (two hundred and sixteen).		sixteenth power) to "216" (two hundred and sixteen). Let's try
	Let's try again.		again.
	Changes from -02 to -03:		Changes from -02 to -03:
	o Aligned the way the premaster secret is derived.		o Aligned the way the premaster secret is derived.
	o Specified that identities must be sent as human-readable UTF-8		o Specified that identities must be sent as human-readable UTF-8
	strings, not in binary formats. Changed reference to RFC 3629		strings, not in binary formats. Changed reference to RFC 3629
	from informative to normative.		from informative to normative.
	o Selected ciphersuite and alert numbers, and updated IANA		o Selected ciphersuite and alert numbers, and updated IANA
End of changes.
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