urbit/base/pub/doc/hoon/library/2ew.md
2015-04-29 18:48:45 -04:00

9.9 KiB

section 2eW, lite number theory

++egcd

GCD

++  egcd                                                ::  schneier's egcd
  |=  [a=@ b=@]
  =+  si
  =+  [c=(sun a) d=(sun b)]
  =+  [u=[c=(sun 1) d=--0] v=[c=--0 d=(sun 1)]]
  |-  ^-  [d=@ u=@ v=@]
  ?:  =(--0 c)
    [(abs d) d.u d.v]
  ::  ?>  ?&  =(c (sum (pro (sun a) c.u) (pro (sun b) c.v)))
  ::          =(d (sum (pro (sun a) d.u) (pro (sun b) d.v)))
  ::      ==
  =+  q=(fra d c)
  %=  $
    c  (dif d (pro q c))
    d  c
    u  [(dif d.u (pro q c.u)) c.u]
    v  [(dif d.v (pro q c.v)) c.v]
  ==
::

Greatest common denominator

~zod/try=> (egcd 20 15)
[d=5 u=2 v=1]
~zod/try=> (egcd 24 16)
[d=8 u=2 v=1]
~zod/try=> (egcd 7 5)
[d=1 u=3 v=6]
~zod/try=> (egcd (shaf ~ %ham) (shaf ~ %sam))
[ d=1
  u=59.983.396.314.566.203.239.184.568.129.921.874.787  
  v=38.716.650.351.034.402.960.165.718.823.532.275.722
]

++pram

Probable prime

++  pram                                                ::  rabin-miller
  |=  a=@  ^-  ?
  ?:  ?|  =(0 (end 0 1 a))
          =(1 a)
          =+  b=1
          |-  ^-  ?
          ?:  =(512 b)
            |
          ?|(=+(c=+((mul 2 b)) &(!=(a c) =(a (mul c (div a c))))) $(b +(b)))
      ==
    |
  =+  ^=  b
      =+  [s=(dec a) t=0]
      |-  ^-  [s=@ t=@]
      ?:  =(0 (end 0 1 s))
        $(s (rsh 0 1 s), t +(t))
      [s t]
  ?>  =((mul s.b (bex t.b)) (dec a))
  =+  c=0
  |-  ^-  ?
  ?:  =(c 64)
    &
  =+  d=(~(raw og (add c a)) (met 0 a))
  =+  e=(~(exp fo a) s.b d)
  ?&  ?|  =(1 e)
          =+  f=0
          |-  ^-  ?
          ?:  =(e (dec a))
            &
          ?:  =(f (dec t.b))
            |
          $(e (~(pro fo a) e e), f +(f))
      ==
      $(c +(c))
  ==
::

Probable prime test

~zod/try=> (pram 31)
%.y
~zod/try=> =+(a=2 |-(?:(=(a 31) ~ [i=(mod 31 a) t=$(a +(a))])))
~[1 1 3 1 1 3 7 4 1 9 7 5 3 1 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1]
~zod/try=> =+(a=2 |-(?:(=(a 31) ~ [i=(mod 30 a) t=$(a +(a))])))
~[0 0 2 0 0 2 6 3 0 8 6 4 2 0 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0]
~zod/try=> (pram 256)
%.n
~zod/try=> (pram (dec (bex 127)))
%.y

++ramp

r-m prime

++  ramp                                                ::  make r-m prime
  |=  [a=@ b=(list ,@) c=@]  ^-  @ux                    ::  [bits snags seed]
  =>  .(c (shas %ramp c))
  =+  d=_@
  |-
  ?:  =((mul 100 a) d)
    ~|(%ar-ramp !!)
  =+  e=(~(raw og c) a)
  ?:  &((levy b |=(f=@ !=(1 (mod e f)))) (pram e))
    e
  $(c +(c), d (shax d))
::

Random a bit prime, which isn't 1 modulo a list of other numbers, using salt c.

~zod/try=> (ramp 20 ~ %hamelok)
0xf.1f0d
~zod/try=> (ramp 20 ~ %hameloe)
0x2.d341
~zod/try=> (ramp 5 ~ %kole)
0x1f
~zod/try=> (ramp 7 ~ %kole)
0x4f
~zod/try=> (ramp 7 ~[0x4e] %kole)
0x43
~zod/try=> `@uw`(ramp 128 ~ %late)
0w3y.irKIL.l-pp1.2CkG4.3lsTF

++fo

Prime engine

++  fo                                                  ::  modulo prime
  |_  a=@

XX DO NOT RERUN GET.LS, THERE EXIST ARM COLLISIONS

Core for performing arithmetic modulo a prime number

~zod/try=> ~(. fo 79)
<7.get [@ud <373.jdd 100.kzl 1.ypj %164>]>

++dif

Difference

  ++  dif
    |=  [b=@ c=@]
    (sit (sub (add a b) (sit c)))
  ::

Subtract

~zod/try=> (~(dif fo 79) 10 5)
5
~zod/try=> (~(dif fo 79) 5 10)
74

++exp

Exponent

  ++  exp
    |=  [b=@ c=@]
    ?:  =(0 b)
      1
    =+  d=$(b (rsh 0 1 b))
    =+  e=(pro d d)
    ?:(=(0 (end 0 1 b)) e (pro c e))
  ::

Exponent

~zod/try=> (~(exp fo 79) 3 5)
46

++fra

Divide

  ++  fra
    |=  [b=@ c=@]
    (pro b (inv c))
  ::

Divide

~zod/try=> (~(fra fo 79) 20 4)
5
~zod/try=> (~(fra fo 79) 7 11)
15

++inv

Inverse

  ++  inv
    |=  b=@
    =+  c=(dul:si u:(egcd b a) a)
    c
  ::

Multiplicative inverse

~zod/try=> (~(inv fo 79) 12)
33
~zod/try=> (~(pro fo 79) 12 33)
1
~zod/try=> (~(inv fo 79) 0)
0

++pro

Product

  ++  pro
    |=  [b=@ c=@]
    (sit (mul b c))
  ::

Product

~zod/try=> (~(pro fo 79) 5 10)
50
~zod/try=> (~(pro fo 79) 5 20)
21

++sit

Bounds

  ++  sit
    |=  b=@
    (mod b a)
  ::

Bounds check

~zod/try=> (~(sit fo 79) 9)
9
~zod/try=> (~(sit fo 79) 99)
20

++sum

Sum

  ++  sum
    |=  [b=@ c=@]
    (sit (add b c))
  --

Add

~zod/try=> (~(sum fo 79) 9 9)
18
~zod/try=> (~(sum fo 79) 70 9)
0

++ga

++  ga                                                  ::  GF (bex p.a)
  |=  a=[p=@ q=@ r=@]                                   ::  dim poly gen
  =+  si=(bex p.a)
  =+  ma=(dec si)
  =>  |%

RSA internals

XX document


++dif

      ++  dif                                           ::  add and sub
        |=  [b=@ c=@]
        ~|  [%dif-ga a]
        ?>  &((lth b si) (lth c si))
        (mix b c)
      ::

XX document


++dub

      ++  dub                                           ::  mul by x
        |=  b=@
        ~|  [%dub-ga a]
        ?>  (lth b si)
        ?:  =(1 (cut 0 [(dec p.a) 1] b))
          (dif (sit q.a) (sit (lsh 0 1 b)))
        (lsh 0 1 b)
      ::

XX document


++pro

      ++  pro                                           ::  slow multiply
        |=  [b=@ c=@]
        ?:  =(0 b)
          0
        ?:  =(1 (dis 1 b))
          (dif c $(b (rsh 0 1 b), c (dub c)))
        $(b (rsh 0 1 b), c (dub c))
      ::

XX document


++toe

      ++  toe                                           ::  exp/log tables
        =+  ^=  nu
            |=  [b=@ c=@]
            ^-  (map ,@ ,@)
            =+  d=*(map ,@ ,@)
            |-
            ?:  =(0 c)
              d
            %=  $
              c  (dec c)
              d  (~(put by d) c b)
            ==
        =+  [p=(nu 0 (bex p.a)) q=(nu ma ma)]
        =+  [b=1 c=0]
        |-  ^-  [p=(map ,@ ,@) q=(map ,@ ,@)]
        ?:  =(ma c)
          [(~(put by p) c b) q]
        %=  $
          b  (pro r.a b)
          c  +(c)
          p  (~(put by p) c b)
          q  (~(put by q) b c)
        ==
      ::

XX document


++sit

      ++  sit                                           ::  reduce
        |=  b=@
        (mod b (bex p.a))
      --

XX document


++fra

  ++  fra                                               ::  divide
    |=  [b=@ c=@]
    (pro b (inv c))
  ::

XX document


++inv

  ++  inv                                               ::  invert
    |=  b=@
    ~|  [%inv-ga a]
    =+  c=(~(get by q) b)
    ?~  c  !!
    =+  d=(~(get by p) (sub ma u.c))
    (need d)
  ::

XX document


++pow

  ++  pow                                               ::  exponent
    |=  [b=@ c=@]
    =+  [d=1 e=c f=0]
    |-
    ?:  =(p.a f)
      d
    ?:  =(1 (cut 0 [f 1] b))
      $(d (pro d e), e (pro e e), f +(f))
    $(e (pro e e), f +(f))
  ::

XX document


++pro

  ++  pro                                               ::  multiply
    |=  [b=@ c=@]
    ~|  [%pro-ga a]
    =+  d=(~(get by q) b)
    ?~  d  0
    =+  e=(~(get by q) c)
    ?~  e  0
    =+  f=(~(get by p) (mod (add u.d u.e) ma))
    (need f)
  --

XX document