Elligator

Chris Froeschl

Definition 1 Legendre Symbol χ
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TODO

Definition 2 Decoding Function Variable c
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Theorem 3 c Property
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Proof

TODO

Definition 4 Decoding Function Variable r
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Theorem 5 r nonzero
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Proof

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Definition 6 Decoding Function Variable d
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Theorem 7 d nonsquare
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Definition 8 Decoding Function Variable u
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Theorem 9 u nonzero
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Proof

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Definition 10 Decoding Function Variable v
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Proof

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Theorem 11 v nonzero
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Proof

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Definition 12 Decoding Function Variable X
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Proof

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Theorem 13 X nonzero
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Proof

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Definition 14 Decoding Function Variable Y

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Theorem 15 Y nonzero
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Proof

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Definition 16 Decoding Function Variable x
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Theorem 17 x defined
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Proof

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Theorem 18 x nonzero
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Proof

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Definition 19 Decoding Function Variable y
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Theorem 20 y defined
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Proof

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Theorem 21 y + 1nonzero
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Proof

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Theorem 22 Variables Product nonzero

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Proof

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Theorem 23 Decoding Function Variables fulfill Specific Equation

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Proof

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Theorem 24 Decoding Function Variables fulfill Curve Equation

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Proof

This obviously follows from what we did so far.

Definition 25 Decoding Function ϕ
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In the situation of Theorem 1, the decoding function for the complete Edwards Curve \(E : x^2 + y^2 = 1 + d x^2 y^2\) is the function \(\phi : \text{F}_q \to E(\text{F}_q)\) defined as follows:

\(\phi (\pm 1) = (0, 1)\); \(\text{if } t \notin \{ \pm 1\} , \quad \text{then} \quad \phi (t) = (x, y)\).

Theorem 26 Preimages of ϕ

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Proof

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Definition 27 Elliptic Curve over Finite Field
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Definition 28 ϕ(F sub q) Property 1
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Definition 29 Inverted Map Variable η
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Definition 30 ϕ(F sub q) Property 2

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Definition 31 ϕ(F sub q) Property 3

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Definition 32 Inverted Map Set ϕ(F sub q)

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Theorem 33 Point on Curve fulfilling properties also in ϕ(F sub q)

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Proof

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Definition 34 Inverted Map Variable X2
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Theorem 35 X2 defined
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Proof

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Definition 36 Inverted Map Variable z

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Theorem 37 z defined
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Proof

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Definition 38 Inverted Map Variable u2
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Theorem 39 z defined
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Proof

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Definition 40 Inverted Map Variable t2
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Theorem 41 t2 defined
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Proof

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Theorem 42 Inverted Map Point to Representative

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Proof

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Definition 43 Binary Digits b
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Definition 44 Set of Potential Representatives S
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Definition 45 Binary to Natural Number Function σ
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Definition 46 Injective Map ι
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Theorem 47 Cardinality of S
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Theorem 48 ι is Injective Map
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Definition 49 Set ι of S
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Theorem 50 ι(S) equals ϕ(F sub q)
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TODO