Proth01 for the HP16C v1 2013-05-12

R0 - 1e17
R1 - 1e18
R2 - multiplier (18 digits, msd & lsd != 0)
R3 - multiplicand (18 digits, msd & lsd != 0)
R4 - modulus (0 : 769; 1 : 7937)
R5 - plain/cipher text

Line LBL Keys Display Comments

001 0 LBL 0 43,22,0
002 HEX 23
003 UNSGN 42,3
004 0 0
005 WSIZE 42 44
006 (*) 1 1 /* PRC: PReCision in Digits (hex) */
007 2 2
008 STO I 44 32
009 1 1
010 1 LBL 1 43,22,1
011 STO 0 44 0
012 A A
013 * 20
014 DSZ 43 23
015 GTO 1 22 1
016 STO 1 44 1
017 DEC 24
018 R/S 31 /* multiplier (18), ENTER */
019 HEX 23 /* multiplicand (19), R/S */
020 ENTER 36
021 ENTER 36
022 1 1
023 AND 42 20 /* last digit of Mpd mod2 = mod */
024 STO 4 44 4
025 R|v 33
026 A A
027 / 10
028 STO 3 44 3 /* actual modless Mpd */
029 X-Y 34
030 STO 2 44 2
031 0 0
032 A LBL A 43,22,A /* main input loop */
033 R/S 31
034 F F
035 F F
036 X-Y 34
037 X>Y 43 3
038 GTO A 22 A /* input greater than FF; ignore */
039 STO 5 44 5
040 5 LBL 5 43,22,5 /* try again */
041 RCL 3 45 3
042 RCL 2 45 2
043 DBLx 43 20
044 RCL 0 45 0
045 DBL/ 43 10
046 RCL 1 45 1
047 X>Y 43 3 /* need to reduce product? */
048 GTO 2 22 2 /* nope */
049 CLx 43 35
050 A A
051 / 10 /* keep reduced product in y */
052 ENTER 36
053 2 LBL 2 43,22,2
054 X-Y 34
055 STO 3 44 3 /* update multiplicand */
056 RCL 4 45 4
057 X=0 43 40 /* mod 769? */
058 GTO 3 22 3
059 X-Y 34 /* get multiplicand back */
060 1 1
061 F F
062 0 0
063 1 1
064 RMD 42 9 /* possible key */
065 1 1
066 F F
067 0 0
068 0 0
069 X!=Y 43 0 /* just not that one */
070 GTO 4 22 4 /* OK */
071 0 0
072 STO 4 44 4 /* switch mods */
073 GTO 5 22 5 /* try again */
074 3 LBL 3 43,22,3 /* mod 769 */
075 X-Y 34 /* get multiplicand back */
076 3 3
077 0 0
078 1 1
079 RMD 42 9 /* possible key */
080 3 3
081 0 0
082 0 0
083 X!=Y 43 0 /* except that one */
084 GTO 4 22 4 /* OK */
085 1 1
086 STO 4 44 4 /* switch mods */
087 GTO 5 22 5 /* try again */
088 4 LBL 4 43,22,4
089 X-Y 34 /* where did that key go? */
090 2 2
091 0 0
092 0 0 /* that's 512 */
093 X-Y 34 /* actual key */
094 - 30
095 RCL 5 45 5 /* next input */
096 - 30
097 F F
098 F F
099 AND 42 20 /* and we're done */
100 ISZ 43 24
101 GTO A 22 A /* for now */
102 F LBL F 43,22,F
103 RCL I 45 32
104 DEC 24
105 R/S 31
106 CLR REG 42 34
107 FLOAT 2 42,45,2
108 CLx 43 35
109 RTN 43 21 /* optional */

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109/p3r13