Network Working Group John Kelsey Category: INTERNET-DRAFT Certicom draft-ietf-syslog-sign-03.txt Expires Mar 2002 Jon Callas September 2001 Wave Systems Corporation Syslog-Sign Protocol draft-ietf-syslog-sign-03.txt Copyright Notice Copyright 2001 by The Internet Society. All Rights Reserved. Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This work is a product of the IETF syslog Working Group. More information about this effort may be found at http://www.ietf.org/html.charters/syslog-charter.html Comments about this draft should be directed to the syslog working group at the mailing list of syslog-sec@employees.org. 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. Abstract This document describes syslog-sign, a mechanism adding origin authentication, message integrity, replay-resistance, message sequencing, and detection of missing messages to syslog. Syslog-sign provides these security features in a way that has Kelsey, Callas Expires March 21, 2002 [Page 1] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 minimal requirements and minimal impact on existing syslog implementations. It is possible to support syslog-sign and gain some of its security attributes by only changing the behavior of the devices generating syslog messages. Some additional processing of the received syslog messages and the syslog-sign messages on the relays and collectors may realize additional security benefits. Kelsey, Callas Expires March 21, 2002 [Page 2] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 Table of Contents Copyright Notice 1 Status of this Memo 1 Abstract 1 Table of Contents 3 1. Introduction 4 2. Signature Block Format and Fields 4 2.1. syslog Packets Containing a Signature Block 4 2.2. Priority 5 2.3. Cookie 6 2.4. Version 6 2.5. Reboot Session ID 6 2.6. Signature Group 6 2.7. Global Block Counter 6 2.8. First Message Number 6 2.9. Count 7 2.10. Hash Block 7 2.11. Signature 7 3. Signature Groups 7 4. Payload and Certificate Blocks 8 4.1. Preliminaries: Key Management and Distribution Issues 8 4.2. Building the Payload Block 9 4.3. Building the Certificate Block 10 5. Redundancy and Flexibility 11 5.1. Redundancy 11 5.1.1. Certificate Blocks 11 5.1.2. Signature Blocks 11 5.2. Flexibility 11 6. Efficient Verification of Logs 12 6.1. Offline Review of Logs 12 6.2. Online Review of Logs 13 7. Security Considerations 14 8. IANA Considerations 15 9. Authors and Working Group Chair 15 10. Acknowledgements 15 11. References 15 12. Full Copyright Statement 16 Kelsey, Callas Expires March 21, 2002 [Page 3] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 1. Introduction Syslog-sign is an enhancement to syslog [RFC3164] that adds origin authentication, message integrity, replay resistance, message sequencing, and detection of missing messages to syslog. This mechanism makes no changes to the syslog packet format but does require strict adherence to that format. A syslog-sign message contains a signature block as the CONTENT field in the HEADER part as defined in Section 4 of [RFC3164]. This signature block contains a separate digital signature for each of a group of previously sent syslog messages. The overall message is also signed as the last value in this message. Each signature block contains, in effect, a detached signature on some number of previously sent messages. While most implementations of syslog involve only a single device as the generator of each message and a single receiver as the collector of each message, provisions need to be made to cover messages being sent to multiple receivers. This is generally performed based upon the Priority value of the individual messages. For example, messages from any Facility with a Severity value of 3, 2, 1 or 0 may be sent to one collector while all messages of Facilities 4, 10, 13, and 14 may be sent to another collector. Appropriate syslog-sign messages must be kept with their proper syslog messages. To address this, syslog-sign utilizes a signature-group. A signature group identifies a group of messages that are all kept together for signing purposes by the device. A signature block always belongs to exactly one signature group and it always signs messages belonging only to that signature group. The receiver of the previous messages may verify that the digital signature of each received message matches the signature contained in the signature block. A collector may process these signature blocks as they arrive, building an authenticated log file. Alternatively, it may store all the log messages in the order they were received. This allows a network operator to authenticate the log file at the time the logs are reviewed. 2. Signature Block Format and Fields Since the device generating the signature block message signs the entire syslog message, it is imperative that the message MUST NOT be changed in transit. In adherence with Section 4 of [RFC3164], a fully formed syslog message containing a PRI part and a HEADER part containing TIMESTAMP and HOSTNAME fields MUST NOT be changed or modified by any relay. 2.1. syslog Packets Containing a Signature Block Signature block messages MUST be completely formed syslog messages. Signature block messages have PRI, HEADER, and MSG parts as described in Sections 4.1.1 and 4.1.3 of [RFC3164]. The PRI part Kelsey, Callas Expires March 21, 2002 [Page 4] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 MUST have a valid Priority value bounded by angled brackets. The HEADER part MUST have a valid TIMESTAMP field as well as a HOSTNAME field. It SHOULD also contain a valid TAG field. It is RECOMMENDED that the TAG field have the value of "syslog " (without the double quotes) to signify that this message was generated by the syslog process. The CONTENT field of the syslog signature block messages have the following fields. The signature block is composed of the following fields. Each field must be printable ASCII, and any binary values are base-64 encoded. Field Size in bytes ----- ---- -- ----- Priority 3 Cookie 8 Version 4 Reboot Session ID 8 Signature Group 3 Global Block Counter 8 First Message Number 8 Count 2 Hash Block variable, size of hash Signature variable These fields are described below. 2.2. Priority The signature group priority field is set depending on the settings described in Section 3 below. This field is 1, 2, or 3 characters in length and is terminated with a space character. The value in this field specifies the version of the syslog-sign protocol and is terminated with a space character. This is extensible to allow for different hash algorithms and signature schemes to be used in the future. The value of this field is calculated by determining the base64 encoding of the protocol version, the hash algorithm and the signature scheme. Protocol Version - 2 bytes with the first version being the ABNF value of %b0000000000000001 to denote Version 1. Kelsey, Callas Expires March 21, 2002 [Page 5] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 Hash Algorithm - 1 byte with the definition that %b00000001 denotes SHA1. [FIPS-180-1] Signature Scheme - 1 byte with the definition that %b00000001 denotes OpenPGP DSA [RFC2440], [DSA94]. As such, the version, hash algorithm and signature scheme may be represented as %h00010101. The priority field will be the base64 encoding of that value with a space character appended. 2.3. Cookie The cookie is a nine-byte sequence to signal that this is a signature block. This sequence is "@#sigSIG " (without the double quotes). 2.4. Version The version is 2 bytes with the first version being the ABNF value of %b0000000000000001 to denote Version 1. 2.5. Reboot Session ID The reboot session ID is a 48-bit quantity encoded in base 64 as eight bytes, which is required to never repeat or decrease in the lifetime of the device. 2.6. Signature Group This is the SIG identifier, described above. It may take on any value from 0-191 inclusive, and is encoded as two bytes in base 64. 2.7. Global Block Counter The global block counter is a 48-bit quantity encoded in base 64 as eight bytes, which is the number of signature blocks sent out by syslog-sign before this one, in this reboot session. Note that this counter crosses signature groups; it allows us to roughly synchronize when two messages were sent, even though they went to different collectors. 2.8. First Message Number This is a 48-bit quantity encoded in base 64 as eight bytes, which is the unique message number within this signature group of the first message whose hash appears in this block. (That is, if this signature group has processed 1000 messages so far, and the 1001st message from this signature group is the first one whose hash appears in this signature block, then this field is 1001.) Kelsey, Callas Expires March 21, 2002 [Page 6] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 2.9. Count The count is a 6-bit quantity encoded in base 64 as one byte, which is the number of message hashes to follow. 2.10. Hash Block The hash block is a block of hashes, each separately encoded in base-64. The hashing algorithm used effectively specified by the Version field determines the size of each hash, but the size MUST NOT be shorter than 160 bits. 2.11. Signature This is a digital signature, encoded in base-64. The Version field effectively specifies the original encoding of the signature. 3. Signature Groups Recall that syslog-sign doesn't alter messages. That means that the signature group of a message doesn't appear anywhere in the message itself. Instead, the device and any intermediate relays use something inside the message to decide where to route it; the device needs to use the same information to decide which signature group a message belongs to. Syslog-sign provides four options for handling signature groups, linking them with PRI values. In all cases, no more than 192 signature groups (0-191) are permitted. In this list, SIG is the signature group, and PRI is the PRI value of the signature and certificate blocks in that signature group. a. '0' -- Only one signature group, SIG = 0, PRI = XXX. The same signature group is used for all certificate and signature blocks, and for all messages. b. '1' -- Each PRI value has its own signature group. Signature and certificate blocks for a given signature group have SIG = PRI for that signature group. c. '2' -- Each signature group contains a range of PRI values. Signature groups are assigned sequentially. A certificate or signature block for a given signature group have its SIG value, and the highest PRI value in that signature group. (That is, if signature group 2 has PRI values in the range 100-191, then all signature group 2's signature and certificate blocks will have PRI=191, and SIG=2. d. '3' -- Signature groups are not assigned with any simple relationship to PRI values. A certificate or signature block in a given signature group will have that group's SIG value, and PRI = XXX. Kelsey, Callas Expires March 21, 2002 [Page 7] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 Note that options (a) and (b) make the SIG value redundant. However, in installations where log messages are forwarded to different collectors based on some complicated criteria (e.g., whether the message text matches some regular expression), the SIG value gives an easy way for relays to decide where to route signature and certificate blocks. This is necessary, since these blocks almost certainly won't match the regular expressions. Options (a) and (d) set the PRI value to XXX for all signature and certificate blocks. This is intended to make it easier to process these syslog messages separately from others handled by a relay. One reasonable way to configure some installations is to have only one signature group, send messages to many collectors, but send a copy of each signature and certificate block to each collector. This won't allow any collector to detect gaps in the messages, but it will allow all messages that arrive at each collector to be put into the right order, and to be verified. 4. Payload and Certificate Blocks Certificate blocks and payload blocks provide key management in syslog-sign. 4.1. Preliminaries: Key Management and Distribution Issues The purpose of certificate blocks is to support key management using public key cryptosystems. All devices send at least one certificate block at the beginning of a new reboot session, carrying useful information about the reboot session. There are three key points to understand about certificate blocks: a. They handle a variable-sized payload, fragmenting it if necessary and transmitting the fragments as legal syslog messages. This payload is built (as described below) at the beginning of a reboot session and is transmitted in pieces with each certificate block carrying a piece. Note that there is exactly one payload block per reboot session. b. The certificate blocks are digitally signed. The device does not sign the payload block, but the signatures on the certificate blocks ensure its authenticity. Note that it may not even be possible to verify the signature on the certificate blocks without the information in the payload block; in this case the payload block is reconstructed, the key is extracted, and then the certificate blocks are verified. (This is necessary even when the payload block carries a certificate, since some other fields of the payload block aren't otherwise verified.) In practice, I expect that most installations will keep the same public key over long periods of time, so that most of the time, it's easy to verify the signatures on the certificate blocks, and use the payload block to provide other Kelsey, Callas Expires March 21, 2002 [Page 8] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 useful per-session information. c. The kind of payload block that is expected is determined by what kind of key material is on the collector that receives it. The device and collector (or offline log viewer) has both some key material (such as a root public key, or predistributed public key), and an acceptable value for the Key Blob Type in the payload block, below. The collector or offline log viewer MUST NOT accept a payload block of the wrong type. 4.2. Building the Payload Block The payload block is built when a new reboot session is started. There is a one-to-one correspondence of reboot sessions to payload blocks. That is, each reboot session has only one payload block, regardless of how many signature groups it may support. The payload block consists of the following: a. Unique identifier of sender; by default, the sender's 128-bit IP address encoded in base-64. b. Full local timestamp for the device, including year if available, at time reboot session started. c. Signature Group Descriptor. This consists of a one-character field specifying how signature groups are assigned. The possibilities are: (i) '0' -- Only one signature group supported. For all signature blocks and certificate blocks, sig == pri == XXX. (ii) '1' -- Each pri value gets its own signature group. For each signature/certificate block, sig == pri. (iii) '2' -- Signature groups are assigned in some way with no simple relationship to pri values; for all signature/certificate blocks, pri = XXX. (iv) '3' -- Signature groups are assigned to ranges of pri values. For each signature/certificate block, pri = largest pri contained within that signature group. d. Highest SIG Value -- a two-byte field base 64 encoded, must be a number between 0 and 191, inclusive. e. Key Blob Type, a one-byte field which holds one of four values: (i) 'C' -- a PKIX certificate. Kelsey, Callas Expires March 21, 2002 [Page 9] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 (ii) 'P' -- an OpenPGP certificate. (iii) 'K' -- the public key whose corresponding private key is being used to sign these messages. (iv) 'N' -- no key information sent; key is predistributed. (v) 'U' -- installation-specific key exchange information f. The key blob, consisting of the raw key data, if any, base-64 encoded. 4.3. Building the Certificate Block The certificate block must get the payload block to the collector. Since certificates can legitimately be much longer than 1024 bytes, each certificate block carries a piece of the payload block. Note that the device MAY make the certificate blocks of any legal length (that is, any length less than 1024 bytes) which will hold all the required fields. Software that processes certificate blocks MUST deal correctly with blocks of any legal length. The certificate block is built as follows: a. A pri value -- this variable-length (one, two, or three byte) value is chosen to ensure that every signature group will get a full set of certificate blocks. b. Cookie -- an eight byte string, "@#sigCer". c. Version -- 12 bits base-64 encoded as two bytes. d. Reboot Session ID -- as above, a 48-bit quantity encoded in base 64 as eight bytes, which is required to never repeat or decrease in the lifetime of the device. e. Signature Group -- 12 bits base-64 encoded as two bytes. f. Total Payload Length -- 32 bits base-64 encoded as six bytes. g. Index into Payload -- 32 bits base-64 encoded as six bytes. h. Fragment Length -- 12 bits base-64 encoded as two bytes. i. Payload Fragment -- a fragment of the payload, as specified by the above fields. j. Signature -- a digital signature on fields a-i. Kelsey, Callas Expires March 21, 2002 [Page 10] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 5. Redundancy and Flexibility There is a general rule that determines how redundancy works and what level of flexibility the device and collector have in message formats: in general, the device is allowed to send signature and certificate blocks multiple times, to send signature and certificate blocks of any legal length, to include fewer hashes in hash blocks, etc. 5.1. Redundancy Syslog messages are sent over unreliable transport, which means that they can be lost in transit. However, the collector must receive signature and certificate blocks or many messages may not be able to be verified. Sending signature and certificate blocks multiple times provides redundancy; since the collector MUST ignore signature/certificate blocks it has already received and authenticated, the device can in principle change its redundancy level for any reason, without communicating this fact to the collector. Although the device isn't constrained in how it decides to send redundant signature and certificate blocks, or even in whether it decides to send along mutliple copies of normal syslog messages, here I define some redundancy parameters below which may be useful in controlling redundant transmission from the device to the collector. 5.1.1. Certificate Blocks certInitialRepeat = number of times each certificate block should be sent before the first message is sent. certResendDelay = maximum time delay in seconds to delay before next redundant sending. certResendCount = maximum number of sent messages to delay before next redundant sending. 5.1.2. Signature Blocks sigNumberResends = number of times a signature block is resent. sigResendDelay = maximum time delay in seconds from original sending to next redundant sending. sigResendCount = maximum number of sent messages to delay before next redundant sending. 5.2. Flexibility The device may change many things about the makeup of signature and Kelsey, Callas Expires March 21, 2002 [Page 11] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 certificate blocks in a given reboot session. The things it cannot change are: * The version * The number or arrangements of signature groups It is legitimate for a device to send our short signature blocks, in order to keep the collector able to verify messages quickly. In general, unless something verified by the payload block or certificate blocks is changed within the reboot session ID, any change is allowed to the signature or certificate blocks during the session. The device may send shorter signature and certificate blocks for 6. Efficient Verification of Logs The logs secured with syslog-sign may either be reviewed online or offline. Online review is somewhat more complicated and computationally expensive, but not prohibitively so. 6.1. Offline Review of Logs When the collector stores logs and reviewed later, they can be authenticated offline just before they are reviewed. Reviewing these logs offline is simple and relatively cheap in terms of resources used, so long as there is enough space available on the reviewing machine. Here, we will consider that the stored log files have already been separated by sender, reboot session ID, and signature group. This can be done very easily with a script file. We then do the following: a. First, we go through the raw log file, and split its contents into three files. Each message in the raw log file is classified as a normal message, a signature block, or a certificate block. Certificate blocks and signature blocks are stored in their own files. Normal messages are stored in a keyed file, indexed on their hash values. b. We sort the certificate block file by index value, and check to see if we have a set of certificate blocks that can reconstruct the payload block. If so, we reconstruct the payload block, verify any key-identifying information, and then use this to verify the signatures on the certificate blocks we've received. When this is done, we have verified the reboot session and key used for the rest of the process. c. We sort the signature block file by firstMessageNumber. We now create an authenticated log file, which will consist of some header information, and then a sequence of message number, message text pairs. We next go through the signature block file. For each signature block in the file, we do the Kelsey, Callas Expires March 21, 2002 [Page 12] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 following: (i) Verify the signature on the block. (ii) For each hashed message in the block: (a) Look up the hash value in the keyed message file. (b) If the message is found, write (message number, message text) to the authenticated log file. (iii) Skip all other signature blocks with the same firstMessageNumber. d. The resulting authenticated log file will contain all messages that have been authenticated, and will indicate (by missing message numbers) all gaps in the authenticated messages. It's pretty easy to see that, assuming sufficient space for building the keyed file, this whole process is linear in the number of messages (generally two seeks, one to write and the other to read, per normal message received), and O(N lg N) in the number of signature blocks. This estimate comes with two caveats: first, the signature blocks will arrive very nearly in sorted order, and so can probably be sorted more cheaply on average than O(N lg N) steps. Second, the signature verification on each signature block will almost certainly be more expensive than the sorting step in practice. We haven't discussed error-recovery, which may be necessary for the certificate blocks. In practice, a very simple error-recovery strategy is probably good enough -- if the payload block doesn't come out as valid, then we can just try an alternate instance of each certificate block, if such are available, until we get the payload block right. It's easy for an attacker to flood us with plausible-looking messages, signature blocks, and certificate blocks. 6.2. Online Review of Logs Some processes on the collector machine may need to monitor log messages in something very close to real-time. This can be done with syslog-sign, though it is somewhat more complex than the offline analysis. This is done as follows: a. We have an output queue, into which we write (message number, message text) pairs which have been authenticated. Again, we'll assume we're handling only one signature group, and only one reboot session ID, at any given time. b. We have three data structures: A queue into which (message number, hash of message) pairs is kept in sorted order, a queue into which (arrival sequence, hash of message) is kept in sorted Kelsey, Callas Expires March 21, 2002 [Page 13] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 order, and a hash table which stores (message text, count) indexed by hash value. In this file, count may be any number greater than zero; when count is zero, the entry in the hash table is cleared. c. We must receive all the certificate blocks before any other processing can really be done. (This is why they're sent first.) Once that's done, any certificate block that arrives is discarded. d. Whenever a normal message arrives, we add (arrival sequence, hash of message) to our message queue. If our hash table has an entry for the message's hash value, we increment its count by one; otherwise, we create a new entry with count = 1. When the message queue is full, we roll the oldest messages off the queue by taking the last entry in the queue, and using it to index the hash table. If that entry has count is 1, we delete the entry in the hash table; otherwise, we decrement its count. We then delete the last entry in the queue. e. Whenever a signature block arrives, we first check to see if the firstMessageNumber value is too old, or if another signature block with that firstMessageNumber has already been received. If so, we discard the signature block unread. Otherwise, we check its signature, and discard it if the signature isn't valid. A signature block contains a sequence of (message number, message hash) pairs. For each pair, we first check to see if the message hash is in the hash table. If so, we write out the (message number, message text) in the authenticated message queue. Otherwise, we write the (message number, message hash) to the message number queue. This generally involves rolling the oldest entry out of this queue: before this is done, that entry's hash value is again searched for in the hash table. If a matching entry is found, the (message number, message text) pair is written out to the authenticated message queue. In either case, the oldest entry is then discarded. f. The result of this is a sequence of messages in the authenticated message queue, each of which has been authenticated, and which are combined with numbers showing their order of original transmission. It's not too hard to see that this whole process is roughly linear in the number of messages, and also in the number of signature blocks received. The process is susceptible to flooding attacks; an attacker can send enough normal messages that the messages roll off their queue before their signature blocks can be processed. 7. Security Considerations * As with any technology involving cryptography, you should check the current literature to determine if any algorithms used here Kelsey, Callas Expires March 21, 2002 [Page 14] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 have been found to be vulnerable to attack. * This specification uses Public Key Cryptography technologies. The proper party or parties must control the private key portion of a public-private key pair. * Certain operations in this specification involve the use of random numbers. An appropriate entropy source should be used to generate these numbers. See [RFC1750]. 8. IANA Considerations As specified in this document, the Priority field contains options for a hash algorithm and signature scheme. Values of zero are reserved. A value of 1 is defined to be SHA-1, and OpenPGP-DSA, respectively. Values 2 through 63 are to be assigned by IANA using the "IETF Consensus" policy defined in RFC2434. Capability Code values 64 through 127 are to be assigned by IANA, using the "First Come First Served" policy defined in RFC2434. Capability Code values 128 through 255 are vendor-specific, and values in this range are not to be assigned by IANA. 9. Authors and Working Group Chair The working group can be contacted via the current chair: Chris Lonvick Cisco Systems Email: clonvick@cisco.com The authors of this draft are: John Kelsey Email: kelsey.j@ix.netcom.com Jon Callas Email: jon@callas.org 10. Acknowledgements The authors wish to thank Alex Brown, Chris Calabrese, Carson Gaspar, Drew Gross, Chris Lonvick, Darrin New, Marshall Rose, Holt Sorenson, Rodney Thayer, and the many Counterpane Internet Security engineering and operations people who commented on various versions of this proposal. 11. References [DSA94] NIST, FIPS PUB 186, "Digital Signature Standard", May 1994. Kelsey, Callas Expires March 21, 2002 [Page 15] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 [FIPS-180-1] "Secure Hash Standard", National Institute of Standards and Technology, U.S. Department Of Commerce, April 1995. Also known as: 59 Fed Reg 35317 (1994). [MENEZES] Alfred Menezes, Paul van Oorschot, and Scott Vanstone, "Handbook of Applied Cryptography," CRC Press, 1996. [RFC1750] D. Eastlake, S. Crocker, and J. Schiller, "Randomness Recommendations for Security", RFC 1750, December 1994. [RFC1983] Malkin, G., "Internet Users' Glossary", FYI 18, RFC 1983, August 1996. [RFC2085] M. Oehler and R. Glenn, "HMAC-MD5 IP Authentication with Replay Prevention", RFC 2085, February 1997. [RFC2104] H. Krawczyk, M. Bellare, and R. Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104 February 1997. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Level", BCP 14, RFC 2119, March 1997. [RFC2434] T. Narten and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 2434, October 1998 [RFC2440] J. Callas, L. Donnerhacke, H. Finney, and R. Thayer,"OpenPGP Message Format", RFC 2440, November 1998. [RFC3164] C. Lonvick, "The BSD Syslog Protocol", RFC 3164, August 2001. [SCHNEIER] Schneier, B., "Applied Cryptography Second Edition: protocols, algorithms, and source code in C", 1996. [SYSLOG-REL] D. New, M. Rose, "Reliable Delivery for syslog", work in progress. 12. Full Copyright Statement Copyright 2001 by The Internet Society. All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any Kelsey, Callas Expires March 21, 2002 [Page 16] INTERNET-DRAFT Syslog-Sign Protocol September 21, 2001 kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Kelsey, Callas Expires March 21, 2002 [Page 17]