import React from "react";
import Entry from "../../components/entry";
import Pseudocode from "../../components/Pseudocode";
import { Styled } from "theme-ui";
import { InlineMath } from "react-katex";
import Link from "../../components/Link";

export default ({ data, location }) => {
  let fpCode = `
  \\begin{algorithm}
  \\caption{ANSI X9.62 Verifiably Random Curves over $\\mathbb{F}_p$}
  \\begin{algorithmic}
  \\INPUT prime field size $p$
  \\OUTPUT bit-string $SEED$ and field elements $a, b \\in \\mathbb{F}_p$ which define an elliptic curve
  \\PROCEDURE{GenerateCurve}{$p$}
  \\STATE Let $t = \\lfloor \\log_{2} p \\rfloor $; Let $s = \\lfloor (t - 1) / 160 \\rfloor $; Let $h = t - 160 s $
  \\STATE Let $SEED$ be a random bit string of at least 160 bits
  \\STATE Let $g = \\vert SEED \\vert $
  \\STATE Let $H = \\text{SHA-1}(SEED) $
  \\STATE Let $c_0$ be the bit string of $h$ rightmost bits of $H$
  \\STATE Let $W_0$ be $c_0$ with leftmost bit set to $0$
  \\FOR{$i = 1$ \\textbf{to} $s$}
    \\STATE Let $W_i = \\text{SHA-1}((SEED + i) \\mod 2^g)$
  \\ENDFOR
  \\STATE Let $W = W_0 \\Vert W_1 \\Vert \\ldots \\Vert W_s$
  \\STATE Let $r = \\sum_{i = 1}^{t} w_i 2^{t - i}$ \\COMMENT{with $w_i$ being the $i$-th bit of $W$ from the left}
  \\STATE Let $(a, b)$ be elements of $ \\mathbb{F}_p $, so that $ r b^2 \\equiv a^3 \\mod p $
  \\IF{$ 4a^3 + 27b^2 \\equiv 0 \\mod p$}
  \\STATE \\textbf{goto} $3$
  \\ENDIF
  \\RETURN ($SEED, a, b$)
  \\ENDPROCEDURE
  \\end{algorithmic}
  \\end{algorithm}`;
  let f2mCode = `
  \\begin{algorithm}
  \\caption{ANSI X9.62 Verifiably Random Curves over $\\mathbb{F}_{2^m}$}
  \\begin{algorithmic}
  \\INPUT field size $q = 2^m$
  \\OUTPUT bit-string $SEED$ and field elements $a, b \\in \\mathbb{F}_{2^m}$ which define an elliptic curve
  \\PROCEDURE{GenerateCurve}{$q = 2^m$}
  \\STATE Let $t = m$; Let $s = \\lfloor (t - 1) / 160 \\rfloor $; Let $h = t - 160 s $
  \\STATE Let $SEED$ be a random bit string of at least 160 bits
  \\STATE Let $g = \\vert SEED \\vert $
  \\STATE Let $H = \\text{SHA-1}(SEED) $
  \\STATE Let $b_0$ be the bit string of $h$ rightmost bits of $H$
  \\FOR{$i = 1$ \\textbf{to} $s$}
    \\STATE Let $b_i = \\text{SHA-1}((SEED + i) \\mod 2^g)$
  \\ENDFOR
  \\STATE Let $b = b_0 \\Vert b_1 \\Vert \\ldots \\Vert b_s \\in \\mathbb{F}_{2^m}$
  \\IF{$b = 0$}
  \\STATE \\textbf{goto} $3$
  \\ENDIF
  \\STATE Let $a$ be random element from $ \\mathbb{F}_{2^m} $
  \\RETURN ($SEED, a, b$)
  \\ENDPROCEDURE
  \\end{algorithmic}
  \\end{algorithm}`;
  return (
    <Entry data={data} location={location} title={"X962"}>
      <Styled.h2>ANSI X9.62</Styled.h2>
      <Styled.p>
        The <b>ANSI X9.62</b> <Link to="#ansi-x962">[1]</Link> standard
        published by the American National Standards Institute provides a way of
        generating verifiably random elliptic curves in its appendices{" "}
        <i>A.3.3.1</i> and <i>A.3.3.2</i>. The curves are presented in the{" "}
        <Link to={"/x962/"}>ANSI X9.62</Link> category.
      </Styled.p>
      <Styled.h3>
        Generating <InlineMath>{`\\mathbb{F}_p`}</InlineMath> curves
      </Styled.h3>
      <pre>
        <Pseudocode
          code={fpCode}
          options={{ lineNumber: true, noEnd: true, captionCount: 0 }}
        />
      </pre>
      <Styled.h3>
        Generating <InlineMath>{`\\mathbb{F}_{2^m}`}</InlineMath> curves
      </Styled.h3>
      <pre>
        <Pseudocode
          code={f2mCode}
          options={{ lineNumber: true, noEnd: true, captionCount: 1 }}
        />
      </pre>
      <Styled.h4>References</Styled.h4>
      <ol>
        <li id="ansi-x962">
          Accredited Standards Committee X9 :{" "}
          <Link to="https://webstore.ansi.org/standards/ascx9/ansix9621998">
            Public Key Cryptography For The Financial Services Industry : The
            Elliptic Curve Digital Signature Algorithm (ECDSA)
          </Link>
        </li>
      </ol>
    </Entry>
  );
};