Network Working Group P. Hoffman Internet-Draft ICANN Intended status: Informational 29 May 2023 Expires: 30 November 2023 Simple Random Candidate Selection draft-hoffman-genarea-random-candidate-selection-00 Abstract This document describes a process to randomly select a subset of candidates from a larger set of candidates. The process uses an unpredictable value can be trusted by all candidates. It uses randomizing based on a hash function to make the description of the process easy to understand. This draft has a GitHub repository (https://github.com/paulehoffman/ draft-hoffman-genarea-random-candidate-selection). Issues and pull requests can be made there. 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 https://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 30 November 2023. Copyright Notice Copyright (c) 2023 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 (https://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 Hoffman Expires 30 November 2023 [Page 1] Internet-Draft Candidate Selection May 2023 extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Earlier Work . . . . . . . . . . . . . . . . . . . . . . 3 2. Overview of the Process . . . . . . . . . . . . . . . . . . . 3 2.1. Basic Steps . . . . . . . . . . . . . . . . . . . . . . . 3 3. Specifics for the Process . . . . . . . . . . . . . . . . . . 4 3.1. Start of Ceremony . . . . . . . . . . . . . . . . . . . . 4 3.2. Name Submission . . . . . . . . . . . . . . . . . . . . . 5 3.3. Closing Submissions . . . . . . . . . . . . . . . . . . . 5 3.4. Selecting _D_ . . . . . . . . . . . . . . . . . . . . . . 6 3.5. Calculating Hashes . . . . . . . . . . . . . . . . . . . 6 3.6. Selecting _S_ Candidates . . . . . . . . . . . . . . . . 6 4. Handling Process Issues . . . . . . . . . . . . . . . . . . . 6 5. Sample Code . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . 11 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction It is common to need to pick a subset of people from a larger group using a random selection method. This is often done on an ad hoc basis, but for some selections, a more formal process is needed, particularly if the people in the larger group don't all trust the administrator of the selection process to be unbiased. This document gives a simple, understandable process that can be done for groups and subsets of arbitrary size. The process is purposely transparent and reproducible. It works with any group of entities that nave names: people, companies, locations, dates ("18 August 2022"), and so on. As a simple example, a future leadership committee will have a fixed size. The members of the committee will be selected from a large pool of volunteers. Someone is in charge of collecting the names of the volunteers and making a randomized selection among them for the leadership committee. They can use the process in this document to make that selection in a way that is both provably random and understandable. Hoffman Expires 30 November 2023 [Page 2] Internet-Draft Candidate Selection May 2023 Due to the formatting used in this document, the reader is encouraged to read the HTML version, although the text version is still usable. 1.1. Earlier Work RFC 3797 [NomCom] defines the process that the IETF uses to select the NomCom each year. It uses a random input to select from a list of candidate names in ASCII using modulo aritmetic the position of the names in alphabetical order. That process has some significant pitfalls described in the document updating RFC 3797, [NomCom-bis]. The process in this document uses a very different selection process to avoid those pitfalls. After this document has passed IETF review, the IETF might consider using the process described here as a replacement for the process in RFC 3797, but the document is valuable even if the IETF does not want to change the NomCom process. 2. Overview of the Process A few terms are used throughout this document: ceremony: The act of collecting names, making the random selection, and publishing the entire process. ceremony administrator (CA): The person who performs the steps of the ceremony. candidate: The person, organization, or other namable entity that is possibly being selected during the ceremony. candidate name: The name selected by each candidate for the selection process. The candidate name is expressed as a string of Unicode characters [Unicode] in UTF-8 format [UTF-8]. difficult-to-predict number (_D_): A publicly-visible number that is not known before the pool of candidates has been closed. Note that this is different from what is normally called a "random number". True random numbers are designed to be nearly impossible to predict, whereas _D_ in this process has weak (but sufficient) randomness. 2.1. Basic Steps The steps in a ceremony that follows this process is given here. See Section 3 for more detail on the steps. Hoffman Expires 30 November 2023 [Page 3] Internet-Draft Candidate Selection May 2023 1. The CA starts the ceremony by performing the following steps at the same time: * Announces an end date for when the pool will be complete. * Announces a later date on which the difficult-to-predict number, _D_, will be selected. * Announces the source where _D_ will be found. * Announces the number of candidates that will be selected (called _S_). * Opens up the pool of candidates for submission. 2. Candidates submit their names to the pool until the closing date. 3. On the closing date, the CA publishes the set of candidate names with the hexadecimal value of the UTF-8 encoding for each candidate name. 4. On the date for selecting _D_, the CA gets _D_ from the announced source. 5. The CA calculates the hashes used to make the selection. They concatenate each candidate name with _D_ (name first, then _D_), uses the SHA-256 hash function [SHA-2] on the new string, and records the value of the output as a UTF-8 string. 6. The CA arranges the set of hash values in alphabetic order from highest to lowest. They then select the _S_ candidates from the top of the list (that is, the names whose hash values are largest). 3. Specifics for the Process 3.1. Start of Ceremony Much of the trust in the selection process is based on the CA not being able to influence the selection. If the CA can choose, or influence, the value of _D_, they can establish the ordering of the differences of the integers. Similarly, if one or more of the candidates can influence the value of _D_, they can increase their chance of being selected. To make the process trustworthy, the value of _D_ must be unrelated to the CA or the candidates, and it must be selected after the list of candidates is completed There are many sources of such values: Hoffman Expires 30 November 2023 [Page 4] Internet-Draft Candidate Selection May 2023 stock market closing values, numbers chosen for large public lotteries, and so on. Section 3.1 of RFC 3797 lists many such sources. The most important things for a ceremony is that the source is announced before the ceremony starts, that all participants and viewers of a ceremony can find the source on the date specified by the CA, and that everyone gets the same value when they go to the source for that day. If the CA chooses to use stock market closing values, a common open source of those values is the Wall Street Journal. For example, the FTSE 100 Index is a long-established index based on 100 stocks; it is sometimes known by its stock ticker as "UXK". The daily closing for the FTSE 100 Index at the Wall Street Journal can currently be found here (https://www.wsj.com/market-data/quotes/index/UK/UKX/historical- prices). Note that the location for sources of daily closing values can change over time. The CA must check that the source they intende to use is still active, and still available when the ceremony starts. 3.2. Name Submission The CA is the sole arbitrator for whether a candidate is allowed to enter the pool. The CA is also the sole arbitrator of what name string (in UTF-8) the candidate can use in the pool. The order that the candidates join the pool does not affect the outcome of the selection process. Said another way, the pool is kept as an unordered set of candidates, not an ordered list of candidates. 3.3. Closing Submissions At the closing of submissions, the CA verifies that the length of the set of candidates in the pool is larger than _S_. If the length is the same as _S_, the rest of the steps are unneeded (and could be confusing), because all candidates will automatically be selected. If the length is shorter than _S_, the ceremony stops because there are too few candidates. The method for publishing the set of candidates is determined by the CA. Figure 3 gives an example of how a CA might publish this information. Hoffman Expires 30 November 2023 [Page 5] Internet-Draft Candidate Selection May 2023 3.4. Selecting _D_ On the day that the CA announced for the selection of _D_, the CA goes the the source they announced and gets _D_. They encode _D_ as a UTF-8 string, which is fairly easy if the source is numeric. In the example of the FTSE 100 from Figure 4, a closing value for the day announced at the beginning of the ceremony might be "7623.10". This would be encoded in UTF-8 as the string of characters whose value is U+373632372e3130. 3.5. Calculating Hashes Different programming libraries have different requirements for the input to hash functions. Section 5 uses the built-in hashlib library in Python, which requires that text strings come with a specified encoding. 3.6. Selecting _S_ Candidates The process of selecting is simply taking the _S_ candidates whose hash value is. This can easily be determined by sorting the text representation of the hash values because in UTF-8 and ASCII, digits have lower codepoints than letters. To complete the process, the CA should publish all known data for the ceremony. This includes _S_, _D_, the hexadecimal value of _D_, all of the information for each candidate, and the full list of selected candidates. Figure 5 shows an example of what this publication might look like. 4. Handling Process Issues Ceremonies don't always go as planned. For example, after a ceremony completes, one or more of the selected candidates might be removed from the selected set due to voluntary withdrawal or established rules (such as no two candidates being from the same geographic region). In such cases, no new ceremony is needed: the CA simply selects the next candidate(s) on the list that is ordered by hash values. (Note that the process in this document is quite different than that in [NomCom] and [NomCom-bis], where unselecting an already-selected candidate can cause a new random selection for all the remaining candidates. Such reestablishing of the candidate pool can cause confusion and hurt among the candidates who were first selected, then later unselected, due to no fault of the their own.) Hoffman Expires 30 November 2023 [Page 6] Internet-Draft Candidate Selection May 2023 Similarly, if after the selection process is completed, the size _S_ of the selected set needs to increase, the CA simply selects the next candidate(s) on the list that is ordered by hash values. 5. Sample Code The following is a list of figures for an implementation of the procedure shown in this document. * The Python script in Figure 1 implements the algorithm from this document. * The file that contains the list of names is shown in Figure 2. (The names are the winners of the Nobel laureates in Literature for 2016 through 2021.) * A file showing the UTF-8 representation of the names from Figure 2 is shown in Figure 3. This file is suitable for showing to the candidates. * The file that contains the _S_ and _D_ on separate lines is shown in Figure 4. * Figure 5 shows the result of running the program with that file as input. #!/usr/bin/env python3 # Program to randomly select some candidates from a group # See draft-hoffman-genarea-reandom-candidate-selection import hashlib, sys from pathlib import Path # Helper function to turn a UTF-8 string into its hex representation def hexify(in_str): return "".join([hex(c)[2:] for c in in_str.encode("utf8")]) # Santity check the input files given on the command line if len(sys.argv) == 1: exit("Must give the name of the candidate file, and possibly " + \ "the selection file, on the command line. Exiting.") candidate_path = Path(sys.argv[1]) if not candidate_path.exists(): exit(f"The file {str(candidate_path)} does not exist. Exiting.") try: file_contents = candidate_path.open(mode="rt", encoding="utf8") except: Hoffman Expires 30 November 2023 [Page 7] Internet-Draft Candidate Selection May 2023 exit("The candidates file do not appear to be in UTF-8. Exiting.") candidate_lines = file_contents.read().splitlines() # See if there is a second file for selecting if len(sys.argv) == 3: run_including_selection = True selection_path = Path(sys.argv[2]) if not selection_path.exists(): exit(f"The file {str(selection_path)} does not exist. Exiting.") try: file_contents = selection_path.open(mode="rt", encoding="utf8") except: exit("The selection file does not appear to be UTF-8. Exiting.") selection_lines = file_contents.read().splitlines() # Extract D and S from the selection file S_str = selection_lines[0] try: S = int(S_str) except: print(f"The first line of the selection file, '{S_str}', " + \ "is not an integer. Exiting.") D_str = selection_lines[1] D_hex = hexify(D_str) else: run_including_selection = False # Get the candidates information C_info = [] c_names = candidate_lines diff_set = set() for C_str in c_names: C_hex = "".join([hex(c)[2:] for c in C_str.encode("utf8")]) if run_including_selection: C_with_D_str = C_str + D_str C_with_D_hex = hexify(C_with_D_str) C_with_D_hash = hashlib.sha256(C_with_D_hex.encode("utf-8")) C_info.append([C_str, C_hex, C_with_D_str, C_with_D_hex, \ C_with_D_hash.hexdigest()]) else: C_info.append([C_str, C_hex]) # Print the results if run_including_selection: print(f"S is {S}") print(f"D is \"{D_str}\"") print(f" U+{D_hex}\n") print("Candidate information, sorted by hash of name including D") selected = [] for this_info in sorted(C_info, key=lambda a: a[4], reverse=True): Hoffman Expires 30 November 2023 [Page 8] Internet-Draft Candidate Selection May 2023 if S > 0: selected.append(this_info[0]) S -= 1 print(f"{this_info[2]}") print(f" U+{this_info[3]}") print(f" {this_info[4]}") print("\nSelected:\n " + "\n ".join(selected)) else: for this_info in C_info: print(f"{this_info[0]}") print(f" U+{this_info[1]}") Figure 1: Example Python code for this procedure Bob Dylan 石黒 一雄 Olga Tokarczuk Peter Handke Louise Glück Abdulrazak Gurnah Figure 2: Sample name list file Bob Dylan U+426f622044796c616e 石黒 一雄 U+e79fb3e9bb9220e4b880e99b84 Olga Tokarczuk U+4f6c676120546f6b6172637a756b Peter Handke U+50657465722048616e646b65 Louise Glück U+4c6f7569736520476cc3bc636b Abdulrazak Gurnah U+416264756c72617a616b204775726e6168 Figure 3: Full information for the names 3 7623.10 Figure 4: Sample selection information file Hoffman Expires 30 November 2023 [Page 9] Internet-Draft Candidate Selection May 2023 S is 3 D is "7623.10" U+373632332e3130 Candidate information, sorted by hash of name including D 石黒 一雄7623.10 U+e79fb3e9bb9220e4b880e99b84373632332e3130 f2e0d3bbd8eac635d799702bead0fbdf07ff79ef94a261789de50e81adb38a13 Louise Glück7623.10 U+4c6f7569736520476cc3bc636b373632332e3130 a54e282cbaa1f29543cd13d9a29e07e3a38413360172b722f8259c2baa3c38dd Peter Handke7623.10 U+50657465722048616e646b65373632332e3130 8bb3bc197c6462b033e4d8e8cf703b13b1c55172572a85d56c639db5c57d3866 Olga Tokarczuk7623.10 U+4f6c676120546f6b6172637a756b373632332e3130 56166c4e0e6ca027f4150bac5ce83fbf5652e440214fd255308472fed9f8fb1b Abdulrazak Gurnah7623.10 U+416264756c72617a616b204775726e6168373632332e3130 340413dc6b2574f5ddc5e88e1c986a229d9defccbae249789b07a5d2337981ff Bob Dylan7623.10 U+426f622044796c616e373632332e3130 05eb403f4f59f5a7b21f5e5a4e8dbfbac59344fd5e8708ab618b5e2ed27a52de Selected: 石黒 一雄 Louise Glück Peter Handke Figure 5: Output of running the program on the list of names and selection information 6. IANA Considerations This document has no IANA considerations. 7. Security Considerations The value _D_ used in this process is explicitly not cryptographically strong; in fact, it might provide only a few bits of randomness. For example, stock indexes that contain many stocks might be predictable after the third digit from the right, meaning that they only have randomness of about 10 bits. A candidate who has a lot of leeway in choosing their name can possibly increase their chance of being selected by as much as 0.1% with such source of randomness. If the CA feels that candidates have too much leeway in selecting their names and is concerned about candidates gaming the ceremony even to that tiny extent, that CA needs to choose a source Hoffman Expires 30 November 2023 [Page 10] Internet-Draft Candidate Selection May 2023 for _D_ with more randomness. Such selection is outside the scope of this document because it would make the process more complicated or less understandable. Instead, this document relies on the CA to only allow sensible representation of candidate names and to accept a tiny chance that candidates can both predict _D_ and be able to change the name they use to reflect that predicted value. 8. References 8.1. Normative References [SHA-2] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms (SHA and SHA-based HMAC and HKDF)", RFC 6234, DOI 10.17487/RFC6234, May 2011, . [Unicode] The Unicode Consortium, "The Unicode Standard (latest version)", n.d., . [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2003, . 8.2. Informative References [NomCom] Eastlake 3rd, D., "Publicly Verifiable Nominations Committee (NomCom) Random Selection", RFC 3797, DOI 10.17487/RFC3797, June 2004, . [NomCom-bis] Eastlake, D. E., "Publicly Verifiable Nominations Committee (NomCom) Random Selection", Work in Progress, Internet-Draft, draft-eastlake-rfc3797bis-02, 16 April 2023, . Author's Address Paul Hoffman ICANN Email: paul.hoffman@icann.org Hoffman Expires 30 November 2023 [Page 11]