Vehicle Identification Number-Based IPv6 Interface Identifier (VIID)
Author(s): Christophe Janneteau, Alexandru Petrescu, Sofiane Imadali
The Vehicle Identification Number (VIN) is a 17 characters alphanumeric code that uniquely identifies a vehicle worldwide. This code is standardized in ISO-3779 and ISO-3780; other standardization bodies' implementation of this code (NHTSA, SAE) is compliant with ISO...
Network Working Group S. Imadali Internet-Draft A. Petrescu Intended status: Informational C. Janneteau Expires: August 19, 2013 CEA February 15, 2013 Vehicle Identification Number-Based IPv6 Interface Identifier (VIID) draft-imadali-its-vinipv6-viid-00.txt Abstract The Vehicle Identification Number (VIN) is a 17 characters alphanumeric code that uniquely identifies a vehicle worldwide. This code is standardized in ISO-3779 and ISO-3780; other standardization bodies' implementation of this code (NHTSA, SAE) is compliant with ISO standards. The VIN is mandatory for each vehicle and used as a unique identity. Some public information related to a vehicle can be obtained knowing its VIN code. An IPv6 address is 128 bit in length and its rightmost bits form the Interface Identifier (IID). When the IPv6 address is used with IPv6- over-Ethernet and Stateless Address Auto-Configuration, the length of the IID is 64 bit. This document presents an experimental method to convert an IPv6 Interface Identifier starting from the VIN code - the VIID. The conversion can be reverted - given a VIID formed from a VIN it easily possible to find out the original VIN. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on August 19, 2013. Copyright Notice Imadali, et al. Expires August 19, 2013 [Page 1] Internet-Draft VIN-based Interface IDs February 2013 Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Abbreviations Used . . . . . . . . . . . . . . . . . . . . 3 2. VIN Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. WMI . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. VDS . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. VIS . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Mapping method . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Initial assumption . . . . . . . . . . . . . . . . . . . . 7 3.2. Detailed algorithm . . . . . . . . . . . . . . . . . . . . 8 3.3. Examples of use . . . . . . . . . . . . . . . . . . . . . 9 4. IPv6 Unicast Addresses . . . . . . . . . . . . . . . . . . . . 9 4.1. IPv6 link-Local Address Mapping . . . . . . . . . . . . . 10 4.2. IPv6 Unicast Address Mapping . . . . . . . . . . . . . . . 10 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . . 11 Appendix A. Base-VIN Numeral System Specification . . . . . . . . 12 A.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 12 A.2. Conversion from decimal to Base-VIN . . . . . . . . . . . 12 A.3. Conversion from Base-VIN to decimal . . . . . . . . . . . 13 A.4. Number of positions . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Imadali, et al. Expires August 19, 2013 [Page 2] Internet-Draft VIN-based Interface IDs February 2013 1. Introduction 1.1. Requirements Language 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 [RFC 2119]. 1.2. Abbreviations Used VIN - Vehicle Identification Number WMI - World Manufacturer Identifier VDS - Vehicle Description Section VIS - Vehicle Identification Section 2. VIN Overview The VIN is a 17 characters alphanumeric code that uniquely identifies a vehicle worldwide. The list of the involved standard documents include : o ISO 3833:1977, "Road vehicles -- Types -- Terms and definitions". This document defines terms relating to some types of road vehicles designated according to certain design and technical characteristics. It Applies to all vehicles designated for road circulation (with exception of agricultural tractors). o ISO 4030:1983, "Road vehicles -- Vehicle identification number (VIN) -- Location and attachment". This document Specifies the requirements for the location and marking of the VIN on motor vehicles, trailers, motorcycles and mopeds as defined in ISO 3833. o ISO 3779:2009, "Road vehicles -- Vehicle identification number (VIN) -- Content and structure". It specifies the content and structure of a VIN in order to establish, on a world-wide basis, a uniform identification numbering system for road vehicles. This document applies to motor vehicles, towed vehicles, motorcycles and mopeds as defined in ISO 3833. o ISO 3780:2009, "Road vehicles -- World manufacturer identifier (WMI) code". It specifies the content and structure of an identifier in order to establish, on a world-wide basis, the identification of road vehicle manufacturers. The WMI constitutes the first section of the VIN described in ISO 3779. ISO 3780:2009 Imadali, et al. Expires August 19, 2013 [Page 3] Internet-Draft VIN-based Interface IDs February 2013 applies to motor vehicles, towed vehicles, motorcycles and mopeds as defined in ISO 3833. The VIN is used to uniquely identify a vehicle and therefore must appear on each vehicle. Some public information related to a vehicle can be obtained knowing its VIN code. This possibility is used in thefts prevention by assisting law enforcement authorities in tracing and recovering parts from stolen motor vehicles, or reporting vehicle history to sell/buy a used car. The VIN is written in 17 alphanumeric characters with a combination of the 10 Arabic numbers and 23 capital letters of the Latin alphabet. Excluded letters are I(i), O(o) and Q(q). This is to avoid confusion between these characters and the numbers 0 and 1. | 1 2 3 4 5 6 7 8 9 0 | |A B C D E F G H J K L M N P R S T U V W X Y Z| Figure 1: Alphabet for the generation of VIN codes Although the definition of the code differs from USA, where the National Highway Traffic Safety Administration (NHTSA) definition is used, and Europe where the ISO is used, both VIN codes are compliant and do not cause confusion. There are some other implementations of the same code, for example within the Society of Automotive Engineers (SAE) and Australian Design Rules (ADR) which are also compliant with the European ISO format of the VIN. The VIN code contains three sections. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | WMI | VDS | VIS | +--------+-----------------+-----------------------+ Figure 2: VIN code sections 2.1. WMI The WMI is 3 digits long and uniquely designates the manufacturer's continent, country, and the unique national identifier. The 3 digit codes are defined within ISO-3780 and the database is maintained by the SAE. A WMI code can be revoked but cannot be used to designate another manufacturer for 30 years after its revocation date. ISO-3780 standard specifies the use of each bit in the WMI code. From the left to the right, the first bit value designates the region of the car manufacturer. Values [A-C] are reserved for Africa, [1-5] Imadali, et al. Expires August 19, 2013 [Page 4] Internet-Draft VIN-based Interface IDs February 2013 for North America, [8-9] for South America, [J-R] for Asia, [S-Z] for Europe and  for Oceania. Multiple alphanumeric values can be assigned for the same region, depending on the needs. Some values are reserved for future use. Second bit indicates a country in the region designated by the first bit. Multiple values are possible for the same country if needed. For example, if the first bit is V (in Europe) and the second bit is one the letters (F to R), then the designated country is France. Unique identity of a country is assured by the combination of these two values. The assigned codes by country are maintained by SAE and listed in ISO-3780. Third character of this section designates a national unique value for the car manufacturer, maintained by national authorities. It is possible to assign more than one value to the manufacturer if needed. Thus, a unique identification of the car manufacturer can be obtained by the combination of the three values. ISO-3780 distinguishes manufacturers building more or less than 500 cars per year. If less, 3rd digit of WMI is set to '9' and positions 12 to 14 (included) form an extended unique manufacturer identifier that identifies all the manufacturers that build less than 500 cars a year in the same country. If the manufacturer builds more than 500 cars a year, it has one or more identification number(s) depending on the needs. For example, "1FA" and "3FA" identifies Ford in USA and Mexico, respectively. "VF3" is one of the WMI codes of French manufacturer Peugeot. 2.2. VDS The VDS is the second part of the VIN code. It is 6 characters long and gives more information about the vehicle. The description of the vehicle is not unique and each manufacturer has its own mapping table for this section; that is, a same character may have different meanings depending on the manufacturer, and sometimes differ upon the vehicle model. The information given by this section may relate to the vehicle weight, the model, the engine type, the body style or the engine power, for example. It is also possible for the manufacturer to fill this section with "dummy" information if it does not want to use it, as spaces (blanks) are not allowed. Therefore, the manufacturer may not rely on this section to complete the unique identification of a vehicle. Last position of this section (9th digit) is called the check digit. Like the TCP checksum, the check digit is the result of a standard Imadali, et al. Expires August 19, 2013 [Page 5] Internet-Draft VIN-based Interface IDs February 2013 algorithm where the values of other positions are used to generate this value. Possible values for the check digit are numbers 0 to 9 and the letter X [CHECK]. 2.3. VIS The VIS is the third section of the VIN code. It is 8 characters long and, combined with the VDS section, uniquely identifies a vehicle within a car manufacturer for 30 years. The combination of the VIS and the WMI section allows to uniquely identify a vehicle worldwide. This section goes from the 10th digit to the 17th. Digit number 10 designates the year model. It is the year during which the vehicle has been manufactured, or the vehicle model year depending on the manufacturer choice. For this digit, the allowed values are 1 to 9 (0 forbidden) and uppercase Latin alphabet letters except I, O, Q, U and Z. Years from 1980 to 2000 are coded with letters from A to Y; years from 2001 to 2009 are represented with digits from 1 to 9; year 2010 and later are represented with letters from A to Y. This representation gives a cycle of 30 years during which a VIS code is guaranteed to be unique. 11th digit of the VIN designates the plant of the manufacturer where the vehicle has been assembled. For example, 'E' refers to 'Kentucky Truck' plant (Jefferson county, Kentucky) and 'T' refers to 'Otosan Kocaeli Assembly' plant (Kocaeli, Turkey), both plants belong to the manufacturer 'Ford'. The same value may represent different plants depending on the manufacturer. Positions 12 to 17 represent the sequential identification part which is unique on the production line and assigned by the car manufacturer. Digits from 12 to 14 (if digit 3 of WMI is '9') represent the rest of the WMI code of the car manufacturer that produces less than 500 cars a year. Otherwise (general case), positions 12 to 17 are considered as a whole and generally considered as a sequential number. ISO-3779:2009 specifies that the last 4 positions must be numeric, which is applied in Europe. In North America (Canada and USA), the last 5 digits must be numeric for some kind of vehicles and only the last 4 digits for the rest. Imadali, et al. Expires August 19, 2013 [Page 6] Internet-Draft VIN-based Interface IDs February 2013 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 +------+-+-+-+-+-+-+-+--+-----+-----+-----+---+---+----+---+---+--+ | ISO | | | | | | 3779 | WMI | VDS | | VIS | +------+-----+----------+-----+-----+-----+-----------------------+ | >500 | | Vehicle |Check|Model|Plant| | |cars a| WMI |Attributes|digit|Year |Code | Sequential Number | | year | | | | | | | +------+-----+----------+-----+-----+-----+------------+----------+ | <500 | | Vehicle |Check|Model|Plant|Manufacturer|Sequential| |cars a| WMI |Attributes|digit|Year |Code | IDentifier | Number | | year | | | | | | | | +------+-----+----------+-----+-----+-----+------------+----------+ Figure 3: Summary of VIN code, sections definition and use 3. Mapping method The VIN code can be split into 3 parts: WMI, VDS, and VIS. Each part gives a partial description of one vehicle's attributes: manufacturer ID, vehicle's description and vehicle's serial ID. This section specifies the algorithm to perform in order to set an IPv6 [RFC4291] Interface Identifier out of a VIN code (VIID). The method used is based on two short and powerful assumptions that allow for the compression of a maximum number of VIN digits in a minimum number of bits. An example illustrates the use of this method. 3.1. Initial assumption The unique identity of a vehicle is set through two sections of the VIN: the WMI (digits 1 to 3, included) and VIS (digits 12 to 17, included). According to ISO 3779:2009, this information may not be enough, but it is certainly mandatory. Specifically, the cases where dummy values are filled in the VDS section (allowed by ISO 3779:2009) makes these two sections the only relevant information known about the vehicle in order to have its unique identity . The VDS section can be recovered in the cases when WMI and VIS sections are known, using a multi-key query on a local database owned by the manufacturer. A reasonable assumption statement (Assumption 1) based on the previous arguments is summarized as follows: Assumption 1: WMI and VIS sections of a VIN code uniquely identify a vehicle Imadali, et al. Expires August 19, 2013 [Page 7] Internet-Draft VIN-based Interface IDs February 2013 3.2. Detailed algorithm In order to convert the alphanumeric VIN into a binary IID, an initial and straightforward two-steps approach consists in following the operation of mapping (transliteration) by the operation of conversion. The VIN alphabet previously described, leaves 33 possible values for every single VIN digit. The mapping operation consists in representing a VIN digit in decimal and the conversion phase consists in converting this decimal to a binary number. Each resulting binary is 6 bits long in order to cover all the possibilities. This initial method is highly inefficient regarding the number of digits converted versus the number of bits used (which is limited to 64 in Ethernet for IID). For instance, converting WMI and VIS sections (a total of 11 digits) would require 66 bits (6*11) which is incompatible with SLAAC operations in Ethernet [RFC2464]. The current proposal specifies the use of a VIN-specific numeral system (cf. Appendix) using only allowed values; that is Arabic numerals (0 to 9) and Latin letters (A to Z) excluding the exceptions (I, O, and Q) in order to generate Base-VIN numbers. As a comparison, Base-36 (radix 36) contains numerals (0-9) and letters (A-Z). Numbers of this system can be converted to other bases (Hex, decimal, octal and binary). Digits are ordered as follows: 0 < 1 ... < 9 < A ... < Y < Z. Base-VIN can be considered as Base-36 system tailored for VIN-related uses. From this proposal derives the below work hypothesis (Assumption 2) that allows us to convert more than a single VIN digit at a time. Assumption 2: VIN codes are numbers written in the Base-VIN system. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | A | B | C| D| E | F | +--------+--------------+--+--+--------+-----------+ Figure 4: Redesign of the VIN code according to sections definitions The compression gain is achieved by converting a value read in Base- VIN to the binary base, rather than mapping/converting separate digits. The restricted set of allowed values for VIN sections helps reducing the number of bits besides preserving the VIN uniqueness property. Sections A, D, E, and F are extracted from the VIN code and converted accordingly. Sections A and E are read in Base-VIN while sections D and F in decimal. The resulting number of bits after conversion is 51 (over 66 with the previous method). Imadali, et al. Expires August 19, 2013 [Page 8] Internet-Draft VIN-based Interface IDs February 2013 In details, section A (WMI) after conversion is 16 bits long (log2 (33^3)); section D (year model) is 5 bits long (log2(30)); section E (first alphanumeric part of the VIS) is 16 bits long (log2 (33^3 )); and section F (second numeric part of the VIS) is 14 bits long (log2(10^4)). This algorithm is reversible: from the converted values (binary), it is possible to compute the initial coded sections (VMI and VIS). This property is the result of the bijectiveness of used operations for conversion between different numeral systems. Privacy consequences are discussed in the security considerations section. 3.3. Examples of use Possible use cases involve classical vehicular IPv6 networking scenarios: in-vehicle communications (Machine-type), inter-vehicles communications (distributed games, social communications enabler), vehicle-to-Infrastructure communications (remote monitoring), and other examples which are not developed in the current draft. 4. IPv6 Unicast Addresses Assumption 1 sets the 64 bits of the Interface Identifier (IID) by converting the WMI and VIS sections of the VIN using assumption 2. Extracted parts, A, D, E, and F are converted separately and the result is 51 bits long. IID is then used with the IPv6 SLAAC address generation to form a topologically correct IPv6 address. Prefix and IID are the two parts that form an IPv6 address [RFC4862]. The above resulting values are included into the 64bits of the IID. Bits 55 and 56 that correspond to U/L bits are set accordingly to the recommendations. The final result is written on 53 bits, from position 64 to 11 (included) of the IID. 11 bits (positions 10 to 0 included) are left blank. Possible uses of these bits include, but not limited to: o When combined with a Duplicate Address Detection (DAD) algorithm, it allows the resolution of possible global IPv6 address collisions. Note that the above proposal can still map 2 additional VIN digits, which gives the possibility to encode 2 VDS digits (for example) if necessary. o Setting more than one interface address of the Router inside a VIN designated vehicle (Mobile Router). For example, using Linux kernel index numbers for internal interface representation, or a any other sequential numbering method. Imadali, et al. Expires August 19, 2013 [Page 9] Internet-Draft VIN-based Interface IDs February 2013 4.1. IPv6 link-Local Address Mapping The IPv6 link-local address [RFC4291] for an Ethernet interface is formed by appending the VIN-based Interface Identifier obtained by the previous algorithm, to the prefix FE80::/64. 10 bits 54 bits 53 bits 11 bits +----------+-----------------------+--------------------+-------+ |1111111010| (zeros) | VIID |(zeros)| +----------+-----------------------+--------------------+-------+ Figure 5: VIN-Based IPv6 Link local address 4.2. IPv6 Unicast Address Mapping The IPv6 unicast address [RFC4291] for an Ethernet interface is formed by appending the VIN-based Interface Identifier obtained by the previous algorithm, to the prefix announced on the link when a Router Advertisement is present, or set manually. 64 bits 53 bits 11 bits +----------------------------------+--------------------+-------+ | Global or ULA Prefix | VIID |(zeros)| +----------------------------------+--------------------+-------+ Figure 6: VIN-Based IPv6 Unicast address 5. Acknowledgements This work has been performed in the framework of the ICT project ICT- 5-258512 EXALTED, which is partly funded by the European Union. The organisations on the source list [CEA] would like to acknowledge the contributions of their colleagues to the project, although the views expressed in this contribution are those of the authors and do not necessarily represent the project. 6. IANA Considerations This memo includes no request to IANA. 7. Security Considerations Collision happens if at least two interfaces try to set the same IPv6 Imadali, et al. Expires August 19, 2013 [Page 10] Internet-Draft VIN-based Interface IDs February 2013 address in the same subnet. The 11 remaining bits using our method can then be used to fix the collision by pulling another adjacent address (2048 possibilities) or using up to 2 additional VDS digits in order to resolve the conflict. The proposed mapping/conversion method strictly applied to ISO-3779 definitions makes a collision highly unlikely but theoretically possible with the use of revoked or forged VIN codes. We recommend the collision avoidance using the 11 remaining bits to complete assumption 1 (uniqueness conservation) in order to use a vehicle's VIN to generate an IID even in these rare exceptions. Privacy is an important requirement for in-vehicle network-to-network communications. State of the art vehicular applications proposals usually disclose accurate information about geographical position, velocity and identity in safety beacons. Even if these advertisements are signed according to IEEE 1609.2, the above VIID proposal does not fit in this category and does not provide mechanisms to protect the in-vehicle network privacy. The focus of this work is to enable in-vehicle networks to exchange packets with VIN-based IPv6 addresses. Uniqueness and collision-avoidance are thus top list requirements for this objective. In order not to exacerbate privacy concerns, VIN-based IPv6 communications should take precautions in advance. For instance, a Caesar ciphering method would map into Base-VIN with substituted values, before VIID generation. A compromise between collisions and privacy expectations should be made in this case. 8. References 8.1. Normative References [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet Networks", RFC2464, December 1998. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC4291, February 2006. [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC4862, September 2007. 8.2. Informative References [CHECK] US Code of Federal Regulations, "PART 565--VEHICLE IDENTIFICATION NUMBER REQUIREMENTS", June 1996, <http:// Imadali, et al. Expires August 19, 2013 [Page 11] Internet-Draft VIN-based Interface IDs February 2013 www.nhtsa.gov/DOT/NHTSA/Rulemaking/Rules/ Associated%20Files/VIN_Final_Rule_April_08.pdf>. Appendix A. Base-VIN Numeral System Specification A.1. Definitions The Base-VIN is the numeral system where all VIN codes belong. A number in Base-VIN is convertible in other numeral systems (decimal, binary, hexadecimal, etc) by simple multiplication operations and vice-versa, with simple division operations. The Base-VIN numeral system contains 33 different ordered digits. Their value in the decimal system goes from 0 to 32, and the symbols used are those defined in the VIN description: One of the letters in the set [ABCDEFGHJKLMNPRSTUVWXYZ] or a numeral in the set . The ordered set of Base-VIN numerals is defined below. [ Decimal|0|1|2|3|4|5|6|7|8|9|10|11|12|13|14|15|16|17] [Base-VIN|0|1|2|3|4|5|6|7|8|9| A| B| C| D| E| F| G| H] [ Decimal|18|19|20|21|22|23|24|25|26|27|28|29|30|31|32] [Base-VIN| J| K| L| M| N| P| R| S| T| U| V| W| X| Y| Z] Figure 7: Base-VIN ordered numbering A.2. Conversion from decimal to Base-VIN A decimal number can be written in the Base-VIN following simple rules using simple division operations. The algorithm is similar to conversion from decimal to other numeral systems (binary for example) and it is defined as an extension of it. Here are the necessary steps: Suppose we have to convert X from decimal system to VIN system. The resulting number is Y 1) Divide X by 33 while the quotient is greater than 33 2) Write the remainder in the Base-VIN numeral system 3) Stop division when the quotient is less than 33 and write it in Base-VIN 4) Read Y backwards from last quotient to first remainder, putting the last quotient in the most significant bit (MSB) and the first remainder in the least significant bit (LSB). Y is now in the Base-VIN numeral system Imadali, et al. Expires August 19, 2013 [Page 12] Internet-Draft VIN-based Interface IDs February 2013 Example: Let us convert 1200 from decimal system to VIN system. o 1200/33 = 36 + 12 ---> 12 is the first remainder. It is C in Base-VIN o 36 is greater than 33, so we shall continue o 36/33 = 1 + 3 ---> 3 is the second remainder. It is 3 in Base-VIN o 1 is less than 33, so this is the end of our algorithm. 1 is 1 in Base-VIN o The result of the conversion is '13C' A.3. Conversion from Base-VIN to decimal A Base-VIN number can be written in the decimal system following simple rules using simple multiplication and power operations. The algorithm is similar to conversion from other numeral systems to decimal (binary for example) and it defined as an extension of it. Here are the necessary steps: Suppose we have to convert 'X' from Base-VIN numeral system to decimal. The resulting number is 'Y'. Let 'n' be the number of positions in X and X(i) the Base-VIN digit of X in ieth position starting from 1, reading the number from the right (LSB) and converted to decimal (from the table above). Then: Y = 0; for (i = n-1; i == 0; i--) Y+=X(i+1)*(33^i); Example: Let us reconvert the result from the previous example, from Base-VIN to decimal. X = 13C, n = 3, LSB = C and MSB = 1. Y = 1*(33^2) + 3*(33^1) + C*(33^0) = 1*(1089) + 3* (33) + 12*(1) = 1200 A.4. Number of positions It is possible to know how many positions are necessary to write a number in the Base-VIN numeral system before doing the conversion from decimal. It is necessary for that to have the immediate power of 33 that is greater than or equal to the decimal number to convert. Imadali, et al. Expires August 19, 2013 [Page 13] Internet-Draft VIN-based Interface IDs February 2013 The number of necessary positions is this power of 33. For example, suppose that you have to convert 1200 from decimal numeral system to Base-VIN. 1200 is immediately less than 33^3 and greater than 33^2. So 1200 will be written in 3 Base-VIN positions after conversion (We saw above that 1200 is actually '13C' in Base-VIN). Authors' Addresses Sofiane Imadali CEA CEA, LIST, Communicating Systems Laboratory, Point Courrier 173 Gif-sur-Yvette, Essonne F-91191 France Phone: +33 0169080727 Email: email@example.com Alexandru Petrescu CEA CEA, LIST, Communicating Systems Laboratory, Point Courrier 173 Gif-sur-Yvette, Essonne F-91191 France Phone: +33 0169089223 Email: firstname.lastname@example.org Christophe Janneteau CEA CEA, LIST, Communicating Systems Laboratory, Point Courrier 173 Gif-sur-Yvette, Essonne F-91191 France Phone: +33 0169089182 Email: email@example.com Imadali, et al. Expires August 19, 2013 [Page 14]