US A1 (19) United States (12) Patent Application Publication (10) Pub. N0.: US 2001/ A1. Chaum (43) Pub. Date: Oct.

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1 US A1 (19) United States (12) Patent Application Publication (10) Pub. N0.: US 2001/ A1 Chaum (43) Pub. Date: Oct. 25, 2001 (54) PHYSICAL AND DIGITAL SECRET BALLOT (52) US. Cl /12 SYSTEMS (76) Inventor: David Chaum, Sherman Oaks, CA (57) ABSTRACT US ( ) Election automation systems are disclosed that allow plural Correspondence Address; entities, for example trustees, to ensure various properties of DAVID CHAUM an election, including correctness of the outcome, by ini SUTTON ST, tially using con?dential information to form printed ballots SHERMAN OAKS, CA (US) and transferring the ballots to voters. Later When voters electronically cast ballots, such as over networks, they use (21) Appl. No.: 09/771,537 the con?dential information and optionally physical ballot structures to authenticate information provided them, (22) Filedi Jall- 29, 2001 including information indicating Whether their votes Were received by the trustees. Voters can also use the information Related US Application Data in ballots to ensure the secrecy of their vote While it is transmitted to the trustees. The trustees can tabulate results (63) Non'provlslonal of provlslonal apphcanot} _NO' While preventing colluding subsets of trustees from being 60/177>_71_7>?led or} Ja_n' 27> 2000' Non'provlslonal able to improperly modify the outcome of the election or of provisional application No. 60/261,290,?led on Violate the Privacy of individual Voters Jan. 13, Some embodiments secure printing from remote locations, Publication Classi?cation authenticate users in distributed systems, authenticate data to users in distributed systems, and address problems With (51) Int. Cl G06F 17/60 conventional voter registration and absentee ballots..2? a <: % wmcww (11 [I Ballots I 4 1

2 Patent Application Publication Oct. 25, 2001 Sheet 1 0f 41 US 2001/ A1 12? a QQOOQ a 100 i % 6 EH

3 Patent Application Publication Oct. 25, 2001 Sheet 2 0f 41 US 2001/ A1 A F OOQQOOL hmmw wmwv. mmmm Nvom mmmw wmwm womhmmé

4 Patent Application Publication Oct. 25, 2001 Sheet 3 0f 41 US 2001/ A1 Make Ballots ' 31/ Cast Votes / 32/ / 331 Agree Ballots to Count Count Ballots

5 Patent Application Publication Oct. 25, 2001 Sheet 4 0f 41 US 2001/ A1 Trust/tees agre? on pnnter security Printer(s) print ballots v 41 Trustees create random shifts and challenge/response pairs per ballot Data in printer(s) destroyed / v 42 J K116 Trustees supply random shifts and - challenge/response F '9 ' 4 pairs to printer 43 / l' 44/ Printer(s) compute combined shift and combined pairs per ballot

6 Patent Application Publication Oct. 25, 2001 Sheet 5 0f 41 US 2001/ A1 Voter recieves ballot with known serial number Trustees reveal corresponding response l i \/51 Voter finds challenge corresponding to vote Voter outputs corresponding challenge I \/52 fraud Voter checks response on ballot T Voter retains receipt part of ballot and/or voter destroys part of ballot; and/or Challenge routed to trustees linked with serial number voter deposits part of ballot into ballot box 58J / l l 54 Fig. 5

7 Patent Application Publication Oct. 25, 2001 Sheet 6 0f 41 US 2001/ A1 At least one party reviews information about registration! eligibility andlor-troting / 61 i (62 / Trustees agree on at least one set of serial numbers for counting

8 Patent Application Publication Oct. 25, 2001 Sheet 7 0f 41 US 2001/ A1 / 71\/ Pre-computation First pass through trustees 72/ / l Second pass through trustees 73 Post-computation

9 atent Application Publication Oct. 25, 2001 Sheet 8 0f 41 US 2001/ A1

10 Patent Application Publication Oct. 25, 2001 Sheet 9 0f 41 US 2001/ A1 Form a pair for each serial number - 91J i For each serial number, determine the power as two raised to the shift position 92 1 JJ I 93/ Raise the second component of each 4 pair to the power determined Supply the list of pairs to the first trustee

11 Patent Application Publication Oct. 25, 2001 Sheet 10 0f 41 US 2001/ A1 / lnitial input from \ pre_computation, successive inputs from output of previous trustee 101/ 104/ Raise the SeCOnd element to a?rst?xed power for this trustee For each serial number, determme a Raise both elements?r? Power as Y0 of each pair to the ralsed t0 Shl? Same random power amount unqiue to the pair / / For each.senai. Successive output to input of next trustee,?nal output from?nal number, raise the second element to the trustee a" in Same?rst power determined / é : order / FIG. 1 0

12 Patent Application Publication Oct. 25, 2001 Sheet 11 0f 41 US 2001/ A1 Initial input from first pass output, successive inputs from output of previous trustee / 111\7 l Raise the second element to the inverse of the second?xed power and the first fixed power r 112 l j Raise both elements of each pair to the same random power unqiue to the pair I. 113 J _ Sort the pairs in lexicographic order of values of the elements / l Successive output to input of next trustee, final output from?nal trustee Fig. 11

13 Patent Application Publication Oct. 25, 2001 Sheet 12 0f 41 US 2001/ A1 / 121 \/ Take input from output of second pass of last trustee Each trustee releases second fixed exponent / 122 \/ l Raise each second element to inverse of the product of all the second fixed exponents,, 123 J Search for the power difference of each pair 124 Fig. 12

14 Patent Application Publication Oct. 25, 2001 Sheet 13 0f 41 US 2001/ A1 C31 ( :12:01 51:11 1:11:10 Fis- 1 3 t1 t2 position pass , g Q g g enin glfase g u us glattpalfe I135 outputs calculated t T gd1,1 g2-2a1d11 t1 4 = >b gd2,1,g1'1a1d :1 gdsn, g1'2a1d3, t2; b2 4 = O 0;; gd4,1, g2'1a1d41 2 = 1

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16 Patent Application Publication Oct. 25, 2001 Sheet 15 0f 41 US 2001/ A1 <empty> Fig. 1 5a <contest 1, candidate 3> <contest 1, candidate 3>, <contest 2, candidate 1> <revote> <empty> 1 <contest 1, candidate 2> <contest 1, candidate 2>, <contest 1, candidate 1> <empty> Fig. 1 5c <style 3> <style 3>, <contest 1, failure> <style 3>, <contest 1, candidate 1> <style 3>, <contest 1, candidate 1>, <contest 3, candidate 3> <style 3>, <contest 1, candidate 1>, <contest 3, candidate 3>, <con?m1> <empty> Flg- 1 <contest 1, candidate 4, countersign selection pending> <contest 1, candidate 4>, <contest 1, candidate 4>, <close, countersign selection pending> <contest 1, candidate 4>, <c ose> <empty> F ig. 15e <P N digit 1> <PIN digit 1>, <PiN digit 2> <P N digit 1>, <P N digit 2>, <PIN digit 3> <PiN digit 1>, <PIN digit 2>, <P N digit 3>, <P N digit 4> [PIN accepted]

17 Patent Application Publication Oct. 25, 2001 Sheet 16 0f 41 US 2001/ A1 Commit to Random Values Per Ballot 165 Make Ballots Commits and Opens correspond? Yes Random Selection of Ballots to Open, Fig. 16 Open Commits for Selected Ballots

18 Patent Application Publication Oct. 25, 2001 Sheet 17 0f 41 US 2001/ A1 :wr F 36 1 m komm QOBQN MQNA.\ \mmm?ompwm mmm?ombwmq.m. 292m? L03: Dom <22 gmzm >Qm3m Sm? m8 3.5% O LmUm '6% 903%. is :wm.\r\ mbsma m.m. Q. 1, 7, t, b c *3

19 Patent Application Publication Oct. 25, 2001 Sheet 18 0f 41 US 2001/ A1 wmwm wwhw mmmw Nmmw mmom < m_ 0 Q A,owwv AIDE Emu Emm. </ m/ Est %m 8E3 E2. 0 mumm wow 0 Qww L <ECDOCT 2% v

20 Patent Application Publication Oct. 25, 2001 Sheet 19 0f 41 US 2001/ A1 193a John Doe 9047/ Jose Smith 6746 Jane Adams 8397 Don Gold // m r 191') 192 ) Fig. 19

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