< draft-josefsson-base-encoding-02.txt		draft-josefsson-base-encoding-03.txt >
	Network Working Group S. Josefsson (editor)		Network Working Group S. Josefsson (editor)
	Internet-Draft Extundo		Internet-Draft November 13, 2001
	Expires: November 2, 2001 May 4, 2001		Expires: May 14, 2002
	Base Encodings		Base Encodings
	draft-josefsson-base-encoding-02.txt		draft-josefsson-base-encoding
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft and is in full conformance with		This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.		all provisions of Section 10 of RFC2026.
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	Distribution of this document is unlimited. Comments and
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	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2001). All Rights Reserved.		Copyright (C) The Internet Society (2001). All Rights Reserved.
	Abstract		Abstract
	This draft contain descriptions of the commonly used base 16, base		This draft contain descriptions of the commonly used base 64, base
	32, and base 64 encoding schemes. It also discusses the use of		32, and base 16 encoding schemes. It also discusses the use of line-
	line-feeds in encoded data, use of padding in encoded data, use of		feeds in encoded data, use of padding in encoded data, use of non-
	non-alphabet characters in encoded data, and use of different		alphabet characters in encoded data, and use of different encoding
	encoding alphabets (where applicable).		alphabets.
	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 RFC 2119 [3].		document are to be interpreted as described in RFC 2119 [3].
	Table of Contents		Table of Contents
	1. Implementation variances . . . . . . . . . . . . . . . . . . . 3		1. Implementation variances . . . . . . . . . . . . . . . . . . . 3
	1.1 Line feeds in encoded data . . . . . . . . . . . . . . . . . . 3		1.1 Line feeds in encoded data . . . . . . . . . . . . . . . . . . 3
	1.2 Padding of encoded data . . . . . . . . . . . . . . . . . . . 3		1.2 Padding of encoded data . . . . . . . . . . . . . . . . . . . 3
	1.3 Interpretation of non-alphabet characters in encoded data . . 3		1.3 Interpretation of non-alphabet characters in encoded data . . 3
	2. Base 64 Encoding . . . . . . . . . . . . . . . . . . . . . . . 4		1.4 Chosing the alphabet . . . . . . . . . . . . . . . . . . . . . 4
	3. Base 32 Encoding . . . . . . . . . . . . . . . . . . . . . . . 6		2. Base 64 Encoding . . . . . . . . . . . . . . . . . . . . . . . 5
	4. Base 16 Encoding . . . . . . . . . . . . . . . . . . . . . . . 8		3. Base 32 Encoding . . . . . . . . . . . . . . . . . . . . . . . 7
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 9		4. Base 16 Encoding . . . . . . . . . . . . . . . . . . . . . . . 9
	References . . . . . . . . . . . . . . . . . . . . . . . . . . 10		5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . 10		5.1 Examples of Base 64 . . . . . . . . . . . . . . . . . . . . . 10
	Full Copyright Statement . . . . . . . . . . . . . . . . . . . 11		6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
			7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 11
			References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . 11
			Full Copyright Statement . . . . . . . . . . . . . . . . . . . 12
	1. Implementation variances		1. Implementation variances
	Base encodings have historically been implemented with some minor		Base encodings have historically been implemented with some minor
	variances. This section's purpose is to describe these variances,		variances. This section describe these differences, and mandate a
	and to mandate a default behaviour, to reduce the possibility for		default behaviour, to reduce the possibility for ambiguity in other
	ambiguity in other documents using base encodings.		documents using base encodings. Optimizations, such as those used in
			PDF's Base 85 encoding, are not discussed.
	1.1 Line feeds in encoded data		1.1 Line feeds in encoded data
	RFC 2045 [4] is often used as a reference for base64 encoding.		RFC 2045 [2] is often used as a reference for base 64 encoding.
	However, RFC2045 does not define "base64" per se, but rather a		However, RFC 2045 does not define "base 64" per se, but rather a
	"base64 Content-Transfer-Encoding" for use within MIME. RFC 2045		"base 64 Content-Transfer-Encoding" for use within MIME. As such,
	enforces a limit on line length of base64 encode data to 76		RFC 2045 enforces a limit on line length of base 64 encode data to 76
	characters.		characters.
	Implementation of specifications using this document as reference		Implementation of specifications using this document as reference for
	for base encodings MUST NOT add line feeds to the encoded data,		base encodings MUST NOT add line feeds to the encoded data, unless
	unless explicitely stated and handled otherwise in said		explicitely stated and handled otherwise in said specifications.
	specifications.
	1.2 Padding of encoded data		1.2 Padding of encoded data
	In some circumstances, the use of padding ("=") in base encoded data		In some circumstances, the use of padding ("=") in base encoded data
	is not required nor used.		is not required nor used.
	Implementation of specifications using this document as reference		Implementation of specifications using this document as reference for
	for base encodings MUST do proper padding to the encoded data,		base encodings MUST do proper padding to the encoded data, unless
	unless explicitely stated and handled otherwise in said		explicitely stated and handled otherwise in said specifications.
	specifications.
	1.3 Interpretation of non-alphabet characters in encoded data		1.3 Interpretation of non-alphabet characters in encoded data
	Base encodings use a specific, reduced, alphabet to encode binary		Base encodings use a specific, reduced, alphabet to encode binary
	data. Non base alphabet characters may exist within base encoded		data. Non base alphabet characters may exist within base encoded
	data, caused by data corruption or by design.		data, caused by data corruption or by design.
	Implementations of specifications using this document as reference		Implementations of specifications using this document as reference
	for base encodings MUST ignore characters outside the base encoding		for base encodings MUST ignore characters outside the base encoding
	alphabet when interpreting base encoded data (``be liberal in what		alphabet when interpreting base encoded data (``be liberal in what
	you accept''), unless explicitely stated and handled otherwise in		you accept''), unless explicitely stated and handled otherwise in
	said specifications.		said specifications.
	(Note that this means, e.g. CRLF-padding after 76 characters		Note that this means that e.g., CRLF-padding after 76 characters
	constitue "non alphabet characters", and should simply be ignored.		constitue "non alphabet characters", and should simply be ignored.
	Also, the pad character, "=", should not be regarded as part of the		Also, the pad character, "=", should not be regarded as part of the
	base alphabet until the end of the string.)		base alphabet until the end of the string. If more than the allowed
			number of pad characters are found at the end of the string, e.g., a
			base 64 string terminated with "===" the excess pad characters should
			preferably be ignored in a robust implementation.
			1.4 Chosing the alphabet
			Different applications have different requirements on the characters
			in the alphabet. Here are a few requirements that determine which
			alphabet should be used:
			o Handled by humans. Characters "0", "O" are easily interchanged,
			as well "1", "l" and "I".
			o Encoded into structures that place other requirements. This
			determines the use of upper- or lowercase alphabets (for case-
			insensitive alphabets such as base 32). For base 64, the non-
			alphanumeric characters (especially "/") may be problematic in
			filenames and URLs.
			o Used as identifiers. Certain characters, notably "+" and "/" in
			the base 64 alphabet, are treated as word-breaks by legacy text
			search/index tools.
			There is no universally accepted alphabet that fulfill all the
			requirements. In this document, we document and name some currently
			used alphabet variances.
	2. Base 64 Encoding		2. Base 64 Encoding
	The following description of base64 is due to [1], [4] and [5].		The following description of base 64 is due to [1], [2], [4] and [5].
			The URL and filename safe base 64 alphabet is due to [8]. (An
			alternative alphabet has been suggested as a URL safe alphabet, which
			used "~" as the 63rd character. However, since this character has
			special meaning in some file system environments, the "URL and
			Filename safe" alphabet below is recommended instead.)
			The Base 64 encoding is designed to represent arbitrary sequences of
			octets in a form that requires case sensitivity but need not be
			humanly readable.
	A 65-character subset of US-ASCII is used, enabling 6 bits to be		A 65-character subset of US-ASCII is used, enabling 6 bits to be
	represented per printable character. (The extra 65th character, "=",		represented per printable character. (The extra 65th character, "=",
	is used to signify a special processing function.)		is used to signify a special processing function.)
	The encoding process represents 24-bit groups of input bits as		The encoding process represents 24-bit groups of input bits as output
	output strings of 4 encoded characters. Proceeding from left to		strings of 4 encoded characters. Proceeding from left to right, a
	right, a 24-bit input group is formed by concatenating 3 8-bit input		24-bit input group is formed by concatenating 3 8-bit input groups.
	groups. These 24 bits are then treated as 4 concatenated 6-bit		These 24 bits are then treated as 4 concatenated 6-bit groups, each
	groups, each of which is translated into a single digit in the base		of which is translated into a single digit in the base 64 alphabet.
	64 alphabet.
	Each 6-bit group is used as an index into an array of 64 printable		Each 6-bit group is used as an index into an array of 64 printable
	characters. The character referenced by the index is placed in the		characters. The character referenced by the index is placed in the
	output string.		output string.
	Table 1: The Base 64 Alphabet		Table 1: The "Canonical" Base 64 Alphabet
	Value Encoding Value Encoding Value Encoding Value Encoding		Value Encoding Value Encoding Value Encoding Value Encoding
	0 A 17 R 34 i 51 z		0 A 17 R 34 i 51 z
	1 B 18 S 35 j 52 0		1 B 18 S 35 j 52 0
	2 C 19 T 36 k 53 1		2 C 19 T 36 k 53 1
	3 D 20 U 37 l 54 2		3 D 20 U 37 l 54 2
	4 E 21 V 38 m 55 3		4 E 21 V 38 m 55 3
	5 F 22 W 39 n 56 4		5 F 22 W 39 n 56 4
	6 G 23 X 40 o 57 5		6 G 23 X 40 o 57 5
	7 H 24 Y 41 p 58 6		7 H 24 Y 41 p 58 6
	8 I 25 Z 42 q 59 7		8 I 25 Z 42 q 59 7
	9 J 26 a 43 r 60 8		9 J 26 a 43 r 60 8
	10 K 27 b 44 s 61 9		10 K 27 b 44 s 61 9
	11 L 28 c 45 t 62 +		11 L 28 c 45 t 62 +
	12 M 29 d 46 u 63 /		12 M 29 d 46 u 63 /
	13 N 30 e 47 v		13 N 30 e 47 v
	14 O 31 f 48 w (pad) =		14 O 31 f 48 w (pad) =
	15 P 32 g 49 x		15 P 32 g 49 x
	16 Q 33 h 50 y		16 Q 33 h 50 y
			Table 2: The "URL and Filename safe" Base 64 Alphabet
			Value Encoding Value Encoding Value Encoding Value Encoding
			0 A 17 R 34 i 51 z
			1 B 18 S 35 j 52 0
			2 C 19 T 36 k 53 1
			3 D 20 U 37 l 54 2
			4 E 21 V 38 m 55 3
			5 F 22 W 39 n 56 4
			6 G 23 X 40 o 57 5
			7 H 24 Y 41 p 58 6
			8 I 25 Z 42 q 59 7
			9 J 26 a 43 r 60 8
			10 K 27 b 44 s 61 9
			11 L 28 c 45 t 62 - (minus)
			12 M 29 d 46 u 63 _ (understrike)
			13 N 30 e 47 v
			14 O 31 f 48 w (pad) =
			15 P 32 g 49 x
			16 Q 33 h 50 y
	Special processing is performed if fewer than 24 bits are available		Special processing is performed if fewer than 24 bits are available
	at the end of the data being encoded. A full encoding quantum is		at the end of the data being encoded. A full encoding quantum is
	always completed at the end of a quantity. When fewer than 24 input		always completed at the end of a quantity. When fewer than 24 input
	bits are available in an input group, zero bits are added (on the		bits are available in an input group, zero bits are added (on the
	right) to form an integral number of 6-bit groups. Padding at the		right) to form an integral number of 6-bit groups. Padding at the
	end of the data is performed using the '=' character. Since all		end of the data is performed using the '=' character. Since all base
	base 64 input is an integral number of octets, only the following		64 input is an integral number of octets, only the following cases
	cases can arise:		can arise:
	(1) the final quantum of encoding input is an integral multiple of		(1) the final quantum of encoding input is an integral multiple of 24
	24 bits; here, the final unit of encoded output will be an integral		bits; here, the final unit of encoded output will be an integral
	multiple of 4 characters with no "=" padding,		multiple of 4 characters with no "=" padding,
	(2) the final quantum of encoding input is exactly 8 bits; here, the		(2) the final quantum of encoding input is exactly 8 bits; here, the
	final unit of encoded output will be two characters followed by two		final unit of encoded output will be two characters followed by two
	"=" padding characters, or		"=" padding characters, or
	(3) the final quantum of encoding input is exactly 16 bits; here,		(3) the final quantum of encoding input is exactly 16 bits; here, the
	the final unit of encoded output will be three characters followed		final unit of encoded output will be three characters followed by one
	by one "=" padding character.		"=" padding character.
	3. Base 32 Encoding		3. Base 32 Encoding
	The following description of base32 is due to [6] (the padding		The following description of base 32 is due to [7] (with corrections)
	section has been corrected though).		and [6] (the "extended hex" alphabet).
	The Base32 encoding is designed to represent arbitrary sequences of		The Base 32 encoding is designed to represent arbitrary sequences of
	octets in a form that needs to be case insensitive but need not be		octets in a form that needs to be case insensitive but need not be
	humanly readable.		humanly readable.
	A 33-character subset of US-ASCII is used, enabling 5 bits to be		A 33-character subset of US-ASCII is used, enabling 5 bits to be
	represented per printable character. (The extra 33rd character, "=",		represented per printable character. (The extra 33rd character, "=",
	is used to signify a special processing function.)		is used to signify a special processing function.)
	The encoding process represents 40-bit groups of input bits as		The encoding process represents 40-bit groups of input bits as output
	output strings of 8 encoded characters. Proceeding from left to		strings of 8 encoded characters. Proceeding from left to right, a
	right, a 40-bit input group is formed by concatenating 5 8bit input		40-bit input group is formed by concatenating 5 8bit input groups.
	groups. These 40 bits are then treated as 8 concatenated 5-bit		These 40 bits are then treated as 8 concatenated 5-bit groups, each
	groups, each of which is translated into a single digit in the		of which is translated into a single digit in the base 32 alphabet.
	base32 alphabet. When encoding a bit stream via the base32		When encoding a bit stream via the base 32 encoding, the bit stream
	encoding, the bit stream must be presumed to be ordered with the		must be presumed to be ordered with the most-significant-bit first.
	most-significant-bit first. That is, the first bit in the stream		That is, the first bit in the stream will be the high-order bit in
	will be the high-order bit in the first 8bit byte, and the eighth		the first 8bit byte, and the eighth bit will be the low-order bit in
	bit will be the low-order bit in the first 8bit byte, and so on.		the first 8bit byte, and so on.
	Each 5-bit group is used as an index into an array of 32 printable		Each 5-bit group is used as an index into an array of 32 printable
	characters. The character referenced by the index is placed in the		characters. The character referenced by the index is placed in the
	output string. These characters, identified in Table 2, below, are		output string. These characters, identified in Table 2, below, are
	selected from US-ASCII digits and uppercase letters.		selected from US-ASCII digits and uppercase letters.
	Table 2: The Base32 Alphabet		Table 3: The "Canonical" Base 32 Alphabet
	Value Encoding Value Encoding Value Encoding Value Encoding		Value Encoding Value Encoding Value Encoding Value Encoding
	0 A 9 J 18 S 27 3		0 A 9 J 18 S 27 3
	1 B 10 K 19 T 28 4		1 B 10 K 19 T 28 4
	2 C 11 L 20 U 29 5		2 C 11 L 20 U 29 5
	3 D 12 M 21 V 30 6		3 D 12 M 21 V 30 6
	4 E 13 N 22 W 31 7		4 E 13 N 22 W 31 7
	5 F 14 O 23 X		5 F 14 O 23 X
	6 G 15 P 24 Y (pad) =		6 G 15 P 24 Y (pad) =
	7 H 16 Q 25 Z		7 H 16 Q 25 Z
	8 I 17 R 26 2		8 I 17 R 26 2
			Table 4: The "Extended Hex" Base 32 Alphabet
			Value Encoding Value Encoding Value Encoding Value Encoding
			0 0 9 9 18 I 27 R
			1 1 10 A 19 J 28 S
			2 2 11 B 20 K 29 T
			3 3 12 C 21 L 30 U
			4 4 13 D 22 M 31 V
			5 5 14 E 23 N
			6 6 15 F 24 O (pad) =
			7 7 16 G 25 P
			8 8 17 H 26 Q
	Special processing is performed if fewer than 40 bits are available		Special processing is performed if fewer than 40 bits are available
	at the end of the data being encoded. A full encoding quantum is		at the end of the data being encoded. A full encoding quantum is
	always completed at the end of a body. When fewer than 40 input		always completed at the end of a body. When fewer than 40 input bits
	bits are available in an input group, zero bits are added (on the		are available in an input group, zero bits are added (on the right)
	right) to form an integral number of 5-bit groups. Padding at the		to form an integral number of 5-bit groups. Padding at the end of
	end of the data is performed using the "=" character. Since all		the data is performed using the "=" character. Since all base 32
	base32 input is an integral number of octets, only the following		input is an integral number of octets, only the following cases can
	cases can arise:		arise:
	(1) the final quantum of encoding input is an integral multiple of		(1) the final quantum of encoding input is an integral multiple of 40
	40 bits; here, the final unit of encoded output will be an integral		bits; here, the final unit of encoded output will be an integral
	multiple of 8 characters with no "=" padding,		multiple of 8 characters with no "=" padding,
	(2) the final quantum of encoding input is exactly 8 bits; here, the		(2) the final quantum of encoding input is exactly 8 bits; here, the
	final unit of encoded output will be two characters followed by six		final unit of encoded output will be two characters followed by six
	"=" padding characters,		"=" padding characters,
	(3) the final quantum of encoding input is exactly 16 bits; here,		(3) the final quantum of encoding input is exactly 16 bits; here, the
	the final unit of encoded output will be four characters followed by		final unit of encoded output will be four characters followed by four
	four "=" padding characters,		"=" padding characters,
	(4) the final quantum of encoding input is exactly 24 bits; here,		(4) the final quantum of encoding input is exactly 24 bits; here, the
	the final unit of encoded output will be five characters followed by		final unit of encoded output will be five characters followed by
	three "=" padding characters, or		three "=" padding characters, or
	(5) the final quantum of encoding input is exactly 32 bits; here,		(5) the final quantum of encoding input is exactly 32 bits; here, the
	the final unit of encoded output will be seven characters followed		final unit of encoded output will be seven characters followed by one
	by one "=" padding character.		"=" padding character.
	Because it is used only for padding at the end of the data, the
	occurrence of any "=" characters may be taken as evidence that the
	end of the data has been reached (without truncation in transit).
	No such assurance is possible, however, when the number of octets
	transmitted was a multiple of three and no "=" characters are
	present.
	4. Base 16 Encoding		4. Base 16 Encoding
	The following description is original but analogous to previous		The following description is original but analogous to previous
	descriptions.		descriptions.
	A 16-character subset of US-ASCII is used, enabling 4 bits to be		A 16-character subset of US-ASCII is used, enabling 4 bits to be
	represented per printable character.		represented per printable character.
	The encoding process represents 8-bit groups (octets) of input bits		The encoding process represents 8-bit groups (octets) of input bits
	as output strings of 2 encoded characters. Proceeding from left to		as output strings of 2 encoded characters. Proceeding from left to
	right, a 8-bit input is taken from the input data. These 8 bits are		right, a 8-bit input is taken from the input data. These 8 bits are
	then treated as 2 concatenated 4-bit groups, each of which is		then treated as 2 concatenated 4-bit groups, each of which is
	translated into a single digit in the base 16 alphabet.		translated into a single digit in the base 16 alphabet.
	Each 4-bit group is used as an index into an array of 16 printable		Each 4-bit group is used as an index into an array of 16 printable
	characters. The character referenced by the index is placed in the		characters. The character referenced by the index is placed in the
	output string.		output string.
	This draft describe two alphabets used with Base 16 encoding, the		This draft describe two alphabets for Base 16 encoding. While the
	first is considered to be more common. A variation of the first,		Hex alphabet is arguable more natural there may be situations with
	"lowercase hex format", uses lower case characters for values 10-15.		special constraints, such as forbidden leading digits in strings,
			which the other may be useful. Both alphabets are to be handled case
			insensitive.
	Table 3: The "Hex" Base 16 Alphabet		Table 5: The "Hex" Base 16 Alphabet
	Value Encoding Value Encoding Value Encoding Value Encoding		Value Encoding Value Encoding Value Encoding Value Encoding
	0 0 4 4 8 8 12 C		0 0 4 4 8 8 12 C
	1 1 5 5 9 9 13 D		1 1 5 5 9 9 13 D
	2 2 6 6 10 A 14 E		2 2 6 6 10 A 14 E
	3 3 7 7 11 B 15 F		3 3 7 7 11 B 15 F
	Table 4: The Canonical Base 16 Alphabet		Table 6: The Canonical Base 16 Alphabet
	Value Encoding Value Encoding Value Encoding Value Encoding		Value Encoding Value Encoding Value Encoding Value Encoding
	0 A 4 E 8 I 12 M		0 A 4 E 8 I 12 M
	1 B 5 F 9 J 13 N		1 B 5 F 9 J 13 N
	2 C 6 G 10 K 14 O		2 C 6 G 10 K 14 O
	3 D 7 H 11 L 15 P		3 D 7 H 11 L 15 P
	Unlike base32 and base64, no special padding is necessery since a		Unlike base 32 and base 64, no special padding is necessery since a
	full code word is always available.		full code word is always available.
	5. Security Considerations		5. Examples
	This draft does not discuss security.		To translate between binary and a base encoding, the input is stored
			in a structure and the output is extracted. The case for base 64 is
			displayed in the following figure, borrowed from [4].
	Acknowledgement		+--first octet--+-second octet--+--third octet--+
			|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
			+-----------+---+-------+-------+---+-----------+
			|5 4 3 2 1 0|5 4 3 2 1 0|5 4 3 2 1 0|5 4 3 2 1 0|
			+--1.index--+--2.index--+--3.index--+--4.index--+
	I'd like to thank Tony Hansen for comments on the draft.		5.1 Examples of Base 64
			This example is from [4].
			Input data: 0x14fb9c03d97e
			Hex: 1 4 f b 9 c | 0 3 d 9 7 e
			8-bit: 00010100 11111011 10011100 | 00000011 11011001
			11111110
			6-bit: 000101 001111 101110 011100 | 000000 111101 100111
			111110
			Decimal: 5 15 46 28 0 61 37 62
			Output: F P u c A 9 l +
			Input data: 0x14fb9c03d9
			Hex: 1 4 f b 9 c | 0 3 d 9
			8-bit: 00010100 11111011 10011100 | 00000011 11011001
			pad with 00
			6-bit: 000101 001111 101110 011100 | 000000 111101 100100
			Decimal: 5 15 46 28 0 61 36
			pad with =
			Output: F P u c A 9 k =
			Input data: 0x14fb9c03
			Hex: 1 4 f b 9 c | 0 3
			8-bit: 00010100 11111011 10011100 | 00000011
			pad with 0000
			6-bit: 000101 001111 101110 011100 | 000000 110000
			Decimal: 5 15 46 28 0 48
			pad with = =
			Output: F P u c A w = =
			6. Security Considerations
			When implementing Base 64 encoding and decoding, care should be made
			not to introduce vulnerabilities to buffer overflows.
			7. Acknowledgement
			I'd like to thank Tony Hansen and Gordon Mohr for comments and
			suggestions.
	References		References
	[1] Linn, J., "Privacy Enhancement for Internet Electronic Mail:		[1] Linn, J., "Privacy enhancement for Internet electronic mail:
	Part I -- Message Encipherment and Authentication Procedures",		Part I - message encipherment and authentication procedures",
	RFC 1113, August 1989.		RFC 1113, August 1989.
	[2] Elz, R., "A Compact Representation of IPv6 Addresses", RFC		[2] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
	1924, April 1996.		Extensions (MIME) Part One: Format of Internet Message Bodies",
			RFC 2045, November 1996.
	[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement		[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
	Levels", RFC 2119, March 1997.		Levels", BCP 14, RFC 2119, March 1997.
	[4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail		[4] Callas, J., Donnerhacke, L., Finney, H. and R. Thayer, "OpenPGP
	Extensions (MIME) Part One: Format of Internet Message Bodies",		Message Format", RFC 2440, November 1998.
	RFC 2045, November 1996.
	[5] Eastlake, D., "Domain Name System Security Extensions", RFC		[5] Eastlake, D., "Domain Name System Security Extensions", RFC
	2535, March 1999.		2535, March 1999.
	[6] Myers, J., "SASL GSSAPI mechanisms", draft		[6] Klyne, G. and L. Masinter, "Identifying Composite Media
	draft-ietf-cat-sasl-gssapi-01, May 2000.		Features", RFC 2938, September 2000.
			[7] Myers, J., "SASL GSSAPI mechanisms", draft draft-ietf-cat-sasl-
			gssapi-01, May 2000.
			[8] Zooko, O., "Post to P2P-hackers mailing list", World Wide Web
			http://zgp.org/pipermail/p2p-hackers/2001-September/000315.html,
			September 2001.
	Author's Address		Author's Address
	Simon Josefsson		Simon Josefsson
	Extundo		Drottningholmsv. 70
	Drottningholmsv„gen 70
	Stockholm 112 42		Stockholm 112 42
	Sweden		Sweden
	Phone: +46 8 6190422
	EMail: simon@josefsson.org		EMail: simon@josefsson.org
	Full Copyright Statement		Full Copyright Statement
	Copyright (C) The Internet Society (2001). All Rights Reserved.		Copyright (C) The Internet Society (2001). All Rights Reserved.
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