4 .TL "Straylight/Edgeware" "Mark Wooding"
5 .TL "Request for Comments: XXXX" "Straylight/Edgeware"
8 .TT XXXX Wooding "April 2003" \
9 "TrIPE: The Trivial IP Encryption Protocol"
11 .TI 0 "Status of this Memo"
13 This memo defines an Experimental Protocol for the Internet community.
14 This memo does not specify an Internet standard of any kind. Discussion
15 and suggestions for improvement are requested. Distribution of this
20 TrIPE is a simple protocol which enables IP datagrams (or other data) to
21 be exchanged between a pair of hosts over a hostile network while
22 maintaining the properties of secrecy and authenticity; i.e., that the
23 content of the datagrams cannot be determined by eavesdroppers on the
24 network, and that either endpoint can determine whether a datagram
25 received is an unaltered copy of one that was sent by the other.
27 While similar services are provided by other protocols (e.g., [IPSEC]),
28 they tend to be very complicated and difficult to analyze (see, for
29 example, [IPSEC-EVAL]). By contrast, TrIPE attempts to get away with
30 doing as little as possible. There are no negotiations to decide which
31 ciphers are to be used: these things are defined in the protocol
32 specification. There is only one key-exchange algorithm defined.
34 In addition to making analysis easier, a simpler protocol also helps
35 reduce the complexity of implementations: this makes implementation
36 errors less likely, and makes auditing an implementation for security
37 holes a more realistic proposition.
41 The key words `MUST', `MUST NOT', `REQUIRED', `SHALL', `SHALL NOT',
42 `SHOULD', `SHOULD NOT', `RECOMMENDED', `MAY', and `OPTIONAL' in this
43 document are to be interpreted as described in [REQ].
45 .T0 "Protocol overview"
47 The TrIPE protocol sets up a secure point-to-point channel between two
48 peer hosts, through which IP datagrams may be passed securely.
50 All TrIPE messages are sent as UDP datagrams. No UDP port has been
51 registered for TrIPE yet.
53 When a pair of peer hosts are made aware of each other, they begin a key
54 negotiation, using an authenticated Diffie-Hellman key exchange
55 protocol. This enables them to agree a
57 a collection of short-term symmetric keys and other parameters (such as
58 sequence numbering spaces). Keysets expire after a fixed amount of
59 time, or after they have been used to encrypt a given amount of data,
60 whichever happens first. Before the current keyset expires, a new key
61 negotation is started, so that the peers can seamlessly start using the
62 new keys before the old ones become invalid.
68 is a collection of symmetric keys and associated state information. The
69 items required, and the symbolic names by which they are described in
73 .B "Incoming and outgoing encryption keys"
83 .T0 "Data representation and notation"
92 .if !'\\$2'.' \ \\$2\c
101 .if !'\\$2'.' \ \\$2\c
105 .SM "\\$1" "\\$2" "\\$3"
109 We need to deal with a number of data items during the protocol.
111 Object names are given in
114 A plain name indicates `our' value; a `primed' name (e.g.,
116 indicates the peer's corresponding value. If a compound data item name
117 is primed, toggle the primed-ness of the components.
119 Data objects are given types which determine their representation in
120 protocol messages. Type names are given in
123 .T1 "Atomic data items"
126 A single octet, representing a value between 0 and 255.
128 A pair of octets, representing a value between 0 and 65535. The more
129 significant octet appears first.
131 Four octets, representing a value between 0 and 4294967295. More
132 significant octets appear first.
133 .DI "STRING \fIn\fR\fB"
138 does not have a numeric value.
140 A nonnegative multiprecision integer. Let
142 be the integer to be represented, and let
144 be the number of octets required to represent
146 in base-256 format with no leading zeroes, except that if
153 is the unique integer such that
154 .ie t 256\*(^(\fIz\fP\-1\*(^) \(<= \fIn\fP < 256\*(^(\fIz\fP\*(^).
155 .el 256^{z-1} <= n < 256^z.
158 then consists of two octets encoding
164 octets which are the base-256 digits of
166 most significant first.
169 .T1 "Structured data items"
173 is a compound object which is simply the concatenation of a number of
174 its component objects. Structures are used directly as messages, and
175 indirectly as things to be hashed or encrypted.
179 . ST STRUCT . kx-cookie
188 consists of the two items
193 . ST STRUCT . msg-packet
201 . ST STRUCT . kx-prechal
208 . ST STRUCT . kx-cookie
212 . SR TEXT . "tripe-cookie"
218 .T0 "Security considerations"
220 This memo describes a cryptographic protocol for ensuring secrecy and
221 integrity of communications between network hosts. From this point of
222 view, it is entirely about security.
224 Before deploying TrIPE on their own systems, administrators ought to
225 satisfy themselves that the cryptographic algorithms used are
226 sufficiently strong for their purposes, and that their implementation of
227 the TrIPE software has come from a trustworthy source. They should also
228 ensure that they have adequate procedures in place for transporting
229 public keys without a risk of them being modified by adversaries.
234 Kent, S., Atkinson, R., `Security Architecture for the Internet
235 Protocol', RFC 2401, November 1998.
238 Ferguson, N., Schneier, B., `A Cryptographic Evaluation of IPsec',
242 Bradner, S., `Key words for use in RFCs to Indicate Requirement Levels',
243 BCP 14, RFC 2119, March 1997.