Reland "Cut down /crypto and switch what is left of it to boringssl".

crypto/p224.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// This is an implementation of the P224 elliptic curve group. It's written to
-// be short and simple rather than fast, although it's still constant-time.
-//
-// See http://www.imperialviolet.org/2010/12/04/ecc.html ([1]) for background.
-
-#include "crypto/p224.h"
-
-#include <string.h>
-
-#include "base/sys_byteorder.h"
-
-namespace {
-
-using base::HostToNet32;
-using base::NetToHost32;
-
-// Field element functions.
-//
-// The field that we're dealing with is ℤ/pℤ where p = 2**224 - 2**96 + 1.
-//
-// Field elements are represented by a FieldElement, which is a typedef to an
-// array of 8 uint32's. The value of a FieldElement, a, is:
-//   a[0] + 2**28·a[1] + 2**56·a[1] + ... + 2**196·a[7]
-//
-// Using 28-bit limbs means that there's only 4 bits of headroom, which is less
-// than we would really like. But it has the useful feature that we hit 2**224
-// exactly, making the reflections during a reduce much nicer.
-
-using crypto::p224::FieldElement;
-
-// kP is the P224 prime.
-const FieldElement kP = {
-  1, 0, 0, 268431360,
-  268435455, 268435455, 268435455, 268435455,
-};
-
-void Contract(FieldElement* inout);
-
-// IsZero returns 0xffffffff if a == 0 mod p and 0 otherwise.
-uint32 IsZero(const FieldElement& a) {
-  FieldElement minimal;
-  memcpy(&minimal, &a, sizeof(minimal));
-  Contract(&minimal);
-
-  uint32 is_zero = 0, is_p = 0;
-  for (unsigned i = 0; i < 8; i++) {
-    is_zero |= minimal[i];
-    is_p |= minimal[i] - kP[i];
-  }
-
-  // If either is_zero or is_p is 0, then we should return 1.
-  is_zero |= is_zero >> 16;
-  is_zero |= is_zero >> 8;
-  is_zero |= is_zero >> 4;
-  is_zero |= is_zero >> 2;
-  is_zero |= is_zero >> 1;
-
-  is_p |= is_p >> 16;
-  is_p |= is_p >> 8;
-  is_p |= is_p >> 4;
-  is_p |= is_p >> 2;
-  is_p |= is_p >> 1;
-
-  // For is_zero and is_p, the LSB is 0 iff all the bits are zero.
-  is_zero &= is_p & 1;
-  is_zero = (~is_zero) << 31;
-  is_zero = static_cast<int32>(is_zero) >> 31;
-  return is_zero;
-}
-
-// Add computes *out = a+b
-//
-// a[i] + b[i] < 2**32
-void Add(FieldElement* out, const FieldElement& a, const FieldElement& b) {
-  for (int i = 0; i < 8; i++) {
-    (*out)[i] = a[i] + b[i];
-  }
-}
-
-static const uint32 kTwo31p3 = (1u<<31) + (1u<<3);
-static const uint32 kTwo31m3 = (1u<<31) - (1u<<3);
-static const uint32 kTwo31m15m3 = (1u<<31) - (1u<<15) - (1u<<3);
-// kZero31ModP is 0 mod p where bit 31 is set in all limbs so that we can
-// subtract smaller amounts without underflow. See the section "Subtraction" in
-// [1] for why.
-static const FieldElement kZero31ModP = {
-  kTwo31p3, kTwo31m3, kTwo31m3, kTwo31m15m3,
-  kTwo31m3, kTwo31m3, kTwo31m3, kTwo31m3
-};
-
-// Subtract computes *out = a-b
-//
-// a[i], b[i] < 2**30
-// out[i] < 2**32
-void Subtract(FieldElement* out, const FieldElement& a, const FieldElement& b) {
-  for (int i = 0; i < 8; i++) {
-    // See the section on "Subtraction" in [1] for details.
-    (*out)[i] = a[i] + kZero31ModP[i] - b[i];
-  }
-}
-
-static const uint64 kTwo63p35 = (1ull<<63) + (1ull<<35);
-static const uint64 kTwo63m35 = (1ull<<63) - (1ull<<35);
-static const uint64 kTwo63m35m19 = (1ull<<63) - (1ull<<35) - (1ull<<19);
-// kZero63ModP is 0 mod p where bit 63 is set in all limbs. See the section
-// "Subtraction" in [1] for why.
-static const uint64 kZero63ModP[8] = {
-  kTwo63p35, kTwo63m35, kTwo63m35, kTwo63m35,
-  kTwo63m35m19, kTwo63m35, kTwo63m35, kTwo63m35,
-};
-
-static const uint32 kBottom28Bits = 0xfffffff;
-
-// LargeFieldElement also represents an element of the field. The limbs are
-// still spaced 28-bits apart and in little-endian order. So the limbs are at
-// 0, 28, 56, ..., 392 bits, each 64-bits wide.
-typedef uint64 LargeFieldElement[15];
-
-// ReduceLarge converts a LargeFieldElement to a FieldElement.
-//
-// in[i] < 2**62
-
-// GCC 4.9 incorrectly vectorizes the first coefficient elimination loop, so
-// disable that optimization via pragma. Don't use the pragma under Clang, since
-// clang doesn't understand it.
-// TODO(wez): Remove this when crbug.com/439566 is fixed.
-#if defined(__GNUC__) && !defined(__clang__)
-#pragma GCC optimize("no-tree-vectorize")
-#endif
-
-void ReduceLarge(FieldElement* out, LargeFieldElement* inptr) {
-  LargeFieldElement& in(*inptr);
-
-  for (int i = 0; i < 8; i++) {
-    in[i] += kZero63ModP[i];
-  }
-
-  // Eliminate the coefficients at 2**224 and greater while maintaining the
-  // same value mod p.
-  for (int i = 14; i >= 8; i--) {
-    in[i-8] -= in[i];  // reflection off the "+1" term of p.
-    in[i-5] += (in[i] & 0xffff) << 12;  // part of the "-2**96" reflection.
-    in[i-4] += in[i] >> 16;  // the rest of the "-2**96" reflection.
-  }
-  in[8] = 0;
-  // in[0..8] < 2**64
-
-  // As the values become small enough, we start to store them in |out| and use
-  // 32-bit operations.
-  for (int i = 1; i < 8; i++) {
-    in[i+1] += in[i] >> 28;
-    (*out)[i] = static_cast<uint32>(in[i] & kBottom28Bits);
-  }
-  // Eliminate the term at 2*224 that we introduced while keeping the same
-  // value mod p.
-  in[0] -= in[8];  // reflection off the "+1" term of p.
-  (*out)[3] += static_cast<uint32>(in[8] & 0xffff) << 12;  // "-2**96" term
-  (*out)[4] += static_cast<uint32>(in[8] >> 16);  // rest of "-2**96" term
-  // in[0] < 2**64
-  // out[3] < 2**29
-  // out[4] < 2**29
-  // out[1,2,5..7] < 2**28
-
-  (*out)[0] = static_cast<uint32>(in[0] & kBottom28Bits);
-  (*out)[1] += static_cast<uint32>((in[0] >> 28) & kBottom28Bits);
-  (*out)[2] += static_cast<uint32>(in[0] >> 56);
-  // out[0] < 2**28
-  // out[1..4] < 2**29
-  // out[5..7] < 2**28
-}
-
-// TODO(wez): Remove this when crbug.com/439566 is fixed.
-#if defined(__GNUC__) && !defined(__clang__)
-// Reenable "tree-vectorize" optimization if it got disabled for ReduceLarge.
-#pragma GCC reset_options
-#endif
-
-// Mul computes *out = a*b
-//
-// a[i] < 2**29, b[i] < 2**30 (or vice versa)
-// out[i] < 2**29
-void Mul(FieldElement* out, const FieldElement& a, const FieldElement& b) {
-  LargeFieldElement tmp;
-  memset(&tmp, 0, sizeof(tmp));
-
-  for (int i = 0; i < 8; i++) {
-    for (int j = 0; j < 8; j++) {
-      tmp[i+j] += static_cast<uint64>(a[i]) * static_cast<uint64>(b[j]);
-    }
-  }
-
-  ReduceLarge(out, &tmp);
-}
-
-// Square computes *out = a*a
-//
-// a[i] < 2**29
-// out[i] < 2**29
-void Square(FieldElement* out, const FieldElement& a) {
-  LargeFieldElement tmp;
-  memset(&tmp, 0, sizeof(tmp));
-
-  for (int i = 0; i < 8; i++) {
-    for (int j = 0; j <= i; j++) {
-      uint64 r = static_cast<uint64>(a[i]) * static_cast<uint64>(a[j]);
-      if (i == j) {
-        tmp[i+j] += r;
-      } else {
-        tmp[i+j] += r << 1;
-      }
-    }
-  }
-
-  ReduceLarge(out, &tmp);
-}
-
-// Reduce reduces the coefficients of in_out to smaller bounds.
-//
-// On entry: a[i] < 2**31 + 2**30
-// On exit: a[i] < 2**29
-void Reduce(FieldElement* in_out) {
-  FieldElement& a = *in_out;
-
-  for (int i = 0; i < 7; i++) {
-    a[i+1] += a[i] >> 28;
-    a[i] &= kBottom28Bits;
-  }
-  uint32 top = a[7] >> 28;
-  a[7] &= kBottom28Bits;
-
-  // top < 2**4
-  // Constant-time: mask = (top != 0) ? 0xffffffff : 0
-  uint32 mask = top;
-  mask |= mask >> 2;
-  mask |= mask >> 1;
-  mask <<= 31;
-  mask = static_cast<uint32>(static_cast<int32>(mask) >> 31);
-
-  // Eliminate top while maintaining the same value mod p.
-  a[0] -= top;
-  a[3] += top << 12;
-
-  // We may have just made a[0] negative but, if we did, then we must
-  // have added something to a[3], thus it's > 2**12. Therefore we can
-  // carry down to a[0].
-  a[3] -= 1 & mask;
-  a[2] += mask & ((1<<28) - 1);
-  a[1] += mask & ((1<<28) - 1);
-  a[0] += mask & (1<<28);
-}
-
-// Invert calcuates *out = in**-1 by computing in**(2**224 - 2**96 - 1), i.e.
-// Fermat's little theorem.
-void Invert(FieldElement* out, const FieldElement& in) {
-  FieldElement f1, f2, f3, f4;
-
-  Square(&f1, in);                        // 2
-  Mul(&f1, f1, in);                       // 2**2 - 1
-  Square(&f1, f1);                        // 2**3 - 2
-  Mul(&f1, f1, in);                       // 2**3 - 1
-  Square(&f2, f1);                        // 2**4 - 2
-  Square(&f2, f2);                        // 2**5 - 4
-  Square(&f2, f2);                        // 2**6 - 8
-  Mul(&f1, f1, f2);                       // 2**6 - 1
-  Square(&f2, f1);                        // 2**7 - 2
-  for (int i = 0; i < 5; i++) {           // 2**12 - 2**6
-    Square(&f2, f2);
-  }
-  Mul(&f2, f2, f1);                       // 2**12 - 1
-  Square(&f3, f2);                        // 2**13 - 2
-  for (int i = 0; i < 11; i++) {          // 2**24 - 2**12
-    Square(&f3, f3);
-  }
-  Mul(&f2, f3, f2);                       // 2**24 - 1
-  Square(&f3, f2);                        // 2**25 - 2
-  for (int i = 0; i < 23; i++) {          // 2**48 - 2**24
-    Square(&f3, f3);
-  }
-  Mul(&f3, f3, f2);                       // 2**48 - 1
-  Square(&f4, f3);                        // 2**49 - 2
-  for (int i = 0; i < 47; i++) {          // 2**96 - 2**48
-    Square(&f4, f4);
-  }
-  Mul(&f3, f3, f4);                       // 2**96 - 1
-  Square(&f4, f3);                        // 2**97 - 2
-  for (int i = 0; i < 23; i++) {          // 2**120 - 2**24
-    Square(&f4, f4);
-  }
-  Mul(&f2, f4, f2);                       // 2**120 - 1
-  for (int i = 0; i < 6; i++) {           // 2**126 - 2**6
-    Square(&f2, f2);
-  }
-  Mul(&f1, f1, f2);                       // 2**126 - 1
-  Square(&f1, f1);                        // 2**127 - 2
-  Mul(&f1, f1, in);                       // 2**127 - 1
-  for (int i = 0; i < 97; i++) {          // 2**224 - 2**97
-    Square(&f1, f1);
-  }
-  Mul(out, f1, f3);                       // 2**224 - 2**96 - 1
-}
-
-// Contract converts a FieldElement to its minimal, distinguished form.
-//
-// On entry, in[i] < 2**29
-// On exit, in[i] < 2**28
-void Contract(FieldElement* inout) {
-  FieldElement& out = *inout;
-
-  // Reduce the coefficients to < 2**28.
-  for (int i = 0; i < 7; i++) {
-    out[i+1] += out[i] >> 28;
-    out[i] &= kBottom28Bits;
-  }
-  uint32 top = out[7] >> 28;
-  out[7] &= kBottom28Bits;
-
-  // Eliminate top while maintaining the same value mod p.
-  out[0] -= top;
-  out[3] += top << 12;
-
-  // We may just have made out[0] negative. So we carry down. If we made
-  // out[0] negative then we know that out[3] is sufficiently positive
-  // because we just added to it.
-  for (int i = 0; i < 3; i++) {
-    uint32 mask = static_cast<uint32>(static_cast<int32>(out[i]) >> 31);
-    out[i] += (1 << 28) & mask;
-    out[i+1] -= 1 & mask;
-  }
-
-  // We might have pushed out[3] over 2**28 so we perform another, partial
-  // carry chain.
-  for (int i = 3; i < 7; i++) {
-    out[i+1] += out[i] >> 28;
-    out[i] &= kBottom28Bits;
-  }
-  top = out[7] >> 28;
-  out[7] &= kBottom28Bits;
-
-  // Eliminate top while maintaining the same value mod p.
-  out[0] -= top;
-  out[3] += top << 12;
-
-  // There are two cases to consider for out[3]:
-  //   1) The first time that we eliminated top, we didn't push out[3] over
-  //      2**28. In this case, the partial carry chain didn't change any values
-  //      and top is zero.
-  //   2) We did push out[3] over 2**28 the first time that we eliminated top.
-  //      The first value of top was in [0..16), therefore, prior to eliminating
-  //      the first top, 0xfff1000 <= out[3] <= 0xfffffff. Therefore, after
-  //      overflowing and being reduced by the second carry chain, out[3] <=
-  //      0xf000. Thus it cannot have overflowed when we eliminated top for the
-  //      second time.
-
-  // Again, we may just have made out[0] negative, so do the same carry down.
-  // As before, if we made out[0] negative then we know that out[3] is
-  // sufficiently positive.
-  for (int i = 0; i < 3; i++) {
-    uint32 mask = static_cast<uint32>(static_cast<int32>(out[i]) >> 31);
-    out[i] += (1 << 28) & mask;
-    out[i+1] -= 1 & mask;
-  }
-
-  // The value is < 2**224, but maybe greater than p. In order to reduce to a
-  // unique, minimal value we see if the value is >= p and, if so, subtract p.
-
-  // First we build a mask from the top four limbs, which must all be
-  // equal to bottom28Bits if the whole value is >= p. If top_4_all_ones
-  // ends up with any zero bits in the bottom 28 bits, then this wasn't
-  // true.
-  uint32 top_4_all_ones = 0xffffffffu;
-  for (int i = 4; i < 8; i++) {
-    top_4_all_ones &= out[i];
-  }
-  top_4_all_ones |= 0xf0000000;
-  // Now we replicate any zero bits to all the bits in top_4_all_ones.
-  top_4_all_ones &= top_4_all_ones >> 16;
-  top_4_all_ones &= top_4_all_ones >> 8;
-  top_4_all_ones &= top_4_all_ones >> 4;
-  top_4_all_ones &= top_4_all_ones >> 2;
-  top_4_all_ones &= top_4_all_ones >> 1;
-  top_4_all_ones =
-      static_cast<uint32>(static_cast<int32>(top_4_all_ones << 31) >> 31);
-
-  // Now we test whether the bottom three limbs are non-zero.
-  uint32 bottom_3_non_zero = out[0] | out[1] | out[2];
-  bottom_3_non_zero |= bottom_3_non_zero >> 16;
-  bottom_3_non_zero |= bottom_3_non_zero >> 8;
-  bottom_3_non_zero |= bottom_3_non_zero >> 4;
-  bottom_3_non_zero |= bottom_3_non_zero >> 2;
-  bottom_3_non_zero |= bottom_3_non_zero >> 1;
-  bottom_3_non_zero =
-      static_cast<uint32>(static_cast<int32>(bottom_3_non_zero) >> 31);
-
-  // Everything depends on the value of out[3].
-  //    If it's > 0xffff000 and top_4_all_ones != 0 then the whole value is >= p
-  //    If it's = 0xffff000 and top_4_all_ones != 0 and bottom_3_non_zero != 0,
-  //      then the whole value is >= p
-  //    If it's < 0xffff000, then the whole value is < p
-  uint32 n = out[3] - 0xffff000;
-  uint32 out_3_equal = n;
-  out_3_equal |= out_3_equal >> 16;
-  out_3_equal |= out_3_equal >> 8;
-  out_3_equal |= out_3_equal >> 4;
-  out_3_equal |= out_3_equal >> 2;
-  out_3_equal |= out_3_equal >> 1;
-  out_3_equal =
-      ~static_cast<uint32>(static_cast<int32>(out_3_equal << 31) >> 31);
-
-  // If out[3] > 0xffff000 then n's MSB will be zero.
-  uint32 out_3_gt = ~static_cast<uint32>(static_cast<int32>(n << 31) >> 31);
-
-  uint32 mask = top_4_all_ones & ((out_3_equal & bottom_3_non_zero) | out_3_gt);
-  out[0] -= 1 & mask;
-  out[3] -= 0xffff000 & mask;
-  out[4] -= 0xfffffff & mask;
-  out[5] -= 0xfffffff & mask;
-  out[6] -= 0xfffffff & mask;
-  out[7] -= 0xfffffff & mask;
-}
-
-
-// Group element functions.
-//
-// These functions deal with group elements. The group is an elliptic curve
-// group with a = -3 defined in FIPS 186-3, section D.2.2.
-
-using crypto::p224::Point;
-
-// kB is parameter of the elliptic curve.
-const FieldElement kB = {
-  55967668, 11768882, 265861671, 185302395,
-  39211076, 180311059, 84673715, 188764328,
-};
-
-void CopyConditional(Point* out, const Point& a, uint32 mask);
-void DoubleJacobian(Point* out, const Point& a);
-
-// AddJacobian computes *out = a+b where a != b.
-void AddJacobian(Point *out,
-                 const Point& a,
-                 const Point& b) {
-  // See http://hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-3.html#addition-add-2007-bl
-  FieldElement z1z1, z2z2, u1, u2, s1, s2, h, i, j, r, v;
-
-  uint32 z1_is_zero = IsZero(a.z);
-  uint32 z2_is_zero = IsZero(b.z);
-
-  // Z1Z1 = Z1²
-  Square(&z1z1, a.z);
-
-  // Z2Z2 = Z2²
-  Square(&z2z2, b.z);
-
-  // U1 = X1*Z2Z2
-  Mul(&u1, a.x, z2z2);
-
-  // U2 = X2*Z1Z1
-  Mul(&u2, b.x, z1z1);
-
-  // S1 = Y1*Z2*Z2Z2
-  Mul(&s1, b.z, z2z2);
-  Mul(&s1, a.y, s1);
-
-  // S2 = Y2*Z1*Z1Z1
-  Mul(&s2, a.z, z1z1);
-  Mul(&s2, b.y, s2);
-
-  // H = U2-U1
-  Subtract(&h, u2, u1);
-  Reduce(&h);
-  uint32 x_equal = IsZero(h);
-
-  // I = (2*H)²
-  for (int j = 0; j < 8; j++) {
-    i[j] = h[j] << 1;
-  }
-  Reduce(&i);
-  Square(&i, i);
-
-  // J = H*I
-  Mul(&j, h, i);
-  // r = 2*(S2-S1)
-  Subtract(&r, s2, s1);
-  Reduce(&r);
-  uint32 y_equal = IsZero(r);
-
-  if (x_equal && y_equal && !z1_is_zero && !z2_is_zero) {
-    // The two input points are the same therefore we must use the dedicated
-    // doubling function as the slope of the line is undefined.
-    DoubleJacobian(out, a);
-    return;
-  }
-
-  for (int i = 0; i < 8; i++) {
-    r[i] <<= 1;
-  }
-  Reduce(&r);
-
-  // V = U1*I
-  Mul(&v, u1, i);
-
-  // Z3 = ((Z1+Z2)²-Z1Z1-Z2Z2)*H
-  Add(&z1z1, z1z1, z2z2);
-  Add(&z2z2, a.z, b.z);
-  Reduce(&z2z2);
-  Square(&z2z2, z2z2);
-  Subtract(&out->z, z2z2, z1z1);
-  Reduce(&out->z);
-  Mul(&out->z, out->z, h);
-
-  // X3 = r²-J-2*V
-  for (int i = 0; i < 8; i++) {
-    z1z1[i] = v[i] << 1;
-  }
-  Add(&z1z1, j, z1z1);
-  Reduce(&z1z1);
-  Square(&out->x, r);
-  Subtract(&out->x, out->x, z1z1);
-  Reduce(&out->x);
-
-  // Y3 = r*(V-X3)-2*S1*J
-  for (int i = 0; i < 8; i++) {
-    s1[i] <<= 1;
-  }
-  Mul(&s1, s1, j);
-  Subtract(&z1z1, v, out->x);
-  Reduce(&z1z1);
-  Mul(&z1z1, z1z1, r);
-  Subtract(&out->y, z1z1, s1);
-  Reduce(&out->y);
-
-  CopyConditional(out, a, z2_is_zero);
-  CopyConditional(out, b, z1_is_zero);
-}
-
-// DoubleJacobian computes *out = a+a.
-void DoubleJacobian(Point* out, const Point& a) {
-  // See http://hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-3.html#doubling-dbl-2001-b
-  FieldElement delta, gamma, beta, alpha, t;
-
-  Square(&delta, a.z);
-  Square(&gamma, a.y);
-  Mul(&beta, a.x, gamma);
-
-  // alpha = 3*(X1-delta)*(X1+delta)
-  Add(&t, a.x, delta);
-  for (int i = 0; i < 8; i++) {
-          t[i] += t[i] << 1;
-  }
-  Reduce(&t);
-  Subtract(&alpha, a.x, delta);
-  Reduce(&alpha);
-  Mul(&alpha, alpha, t);
-
-  // Z3 = (Y1+Z1)²-gamma-delta
-  Add(&out->z, a.y, a.z);
-  Reduce(&out->z);
-  Square(&out->z, out->z);
-  Subtract(&out->z, out->z, gamma);
-  Reduce(&out->z);
-  Subtract(&out->z, out->z, delta);
-  Reduce(&out->z);
-
-  // X3 = alpha²-8*beta
-  for (int i = 0; i < 8; i++) {
-          delta[i] = beta[i] << 3;
-  }
-  Reduce(&delta);
-  Square(&out->x, alpha);
-  Subtract(&out->x, out->x, delta);
-  Reduce(&out->x);
-
-  // Y3 = alpha*(4*beta-X3)-8*gamma²
-  for (int i = 0; i < 8; i++) {
-          beta[i] <<= 2;
-  }
-  Reduce(&beta);
-  Subtract(&beta, beta, out->x);
-  Reduce(&beta);
-  Square(&gamma, gamma);
-  for (int i = 0; i < 8; i++) {
-          gamma[i] <<= 3;
-  }
-  Reduce(&gamma);
-  Mul(&out->y, alpha, beta);
-  Subtract(&out->y, out->y, gamma);
-  Reduce(&out->y);
-}
-
-// CopyConditional sets *out=a if mask is 0xffffffff. mask must be either 0 of
-// 0xffffffff.
-void CopyConditional(Point* out,
-                     const Point& a,
-                     uint32 mask) {
-  for (int i = 0; i < 8; i++) {
-    out->x[i] ^= mask & (a.x[i] ^ out->x[i]);
-    out->y[i] ^= mask & (a.y[i] ^ out->y[i]);
-    out->z[i] ^= mask & (a.z[i] ^ out->z[i]);
-  }
-}
-
-// ScalarMult calculates *out = a*scalar where scalar is a big-endian number of
-// length scalar_len and != 0.
-void ScalarMult(Point* out, const Point& a,
-                const uint8* scalar, size_t scalar_len) {
-  memset(out, 0, sizeof(*out));
-  Point tmp;
-
-  for (size_t i = 0; i < scalar_len; i++) {
-    for (unsigned int bit_num = 0; bit_num < 8; bit_num++) {
-      DoubleJacobian(out, *out);
-      uint32 bit = static_cast<uint32>(static_cast<int32>(
-          (((scalar[i] >> (7 - bit_num)) & 1) << 31) >> 31));
-      AddJacobian(&tmp, a, *out);
-      CopyConditional(out, tmp, bit);
-    }
-  }
-}
-
-// Get224Bits reads 7 words from in and scatters their contents in
-// little-endian form into 8 words at out, 28 bits per output word.
-void Get224Bits(uint32* out, const uint32* in) {
-  out[0] = NetToHost32(in[6]) & kBottom28Bits;
-  out[1] = ((NetToHost32(in[5]) << 4) |
-            (NetToHost32(in[6]) >> 28)) & kBottom28Bits;
-  out[2] = ((NetToHost32(in[4]) << 8) |
-            (NetToHost32(in[5]) >> 24)) & kBottom28Bits;
-  out[3] = ((NetToHost32(in[3]) << 12) |
-            (NetToHost32(in[4]) >> 20)) & kBottom28Bits;
-  out[4] = ((NetToHost32(in[2]) << 16) |
-            (NetToHost32(in[3]) >> 16)) & kBottom28Bits;
-  out[5] = ((NetToHost32(in[1]) << 20) |
-            (NetToHost32(in[2]) >> 12)) & kBottom28Bits;
-  out[6] = ((NetToHost32(in[0]) << 24) |
-            (NetToHost32(in[1]) >> 8)) & kBottom28Bits;
-  out[7] = (NetToHost32(in[0]) >> 4) & kBottom28Bits;
-}
-
-// Put224Bits performs the inverse operation to Get224Bits: taking 28 bits from
-// each of 8 input words and writing them in big-endian order to 7 words at
-// out.
-void Put224Bits(uint32* out, const uint32* in) {
-  out[6] = HostToNet32((in[0] >> 0) | (in[1] << 28));
-  out[5] = HostToNet32((in[1] >> 4) | (in[2] << 24));
-  out[4] = HostToNet32((in[2] >> 8) | (in[3] << 20));
-  out[3] = HostToNet32((in[3] >> 12) | (in[4] << 16));
-  out[2] = HostToNet32((in[4] >> 16) | (in[5] << 12));
-  out[1] = HostToNet32((in[5] >> 20) | (in[6] << 8));
-  out[0] = HostToNet32((in[6] >> 24) | (in[7] << 4));
-}
-
-}  // anonymous namespace
-
-namespace crypto {
-
-namespace p224 {
-
-bool Point::SetFromString(const base::StringPiece& in) {
-  if (in.size() != 2*28)
-    return false;
-  const uint32* inwords = reinterpret_cast<const uint32*>(in.data());
-  Get224Bits(x, inwords);
-  Get224Bits(y, inwords + 7);
-  memset(&z, 0, sizeof(z));
-  z[0] = 1;
-
-  // Check that the point is on the curve, i.e. that y² = x³ - 3x + b.
-  FieldElement lhs;
-  Square(&lhs, y);
-  Contract(&lhs);
-
-  FieldElement rhs;
-  Square(&rhs, x);
-  Mul(&rhs, x, rhs);
-
-  FieldElement three_x;
-  for (int i = 0; i < 8; i++) {
-    three_x[i] = x[i] * 3;
-  }
-  Reduce(&three_x);
-  Subtract(&rhs, rhs, three_x);
-  Reduce(&rhs);
-
-  ::Add(&rhs, rhs, kB);
-  Contract(&rhs);
-  return memcmp(&lhs, &rhs, sizeof(lhs)) == 0;
-}
-
-std::string Point::ToString() const {
-  FieldElement zinv, zinv_sq, x, y;
-
-  // If this is the point at infinity we return a string of all zeros.
-  if (IsZero(this->z)) {
-    static const char zeros[56] = {0};
-    return std::string(zeros, sizeof(zeros));
-  }
-
-  Invert(&zinv, this->z);
-  Square(&zinv_sq, zinv);
-  Mul(&x, this->x, zinv_sq);
-  Mul(&zinv_sq, zinv_sq, zinv);
-  Mul(&y, this->y, zinv_sq);
-
-  Contract(&x);
-  Contract(&y);
-
-  uint32 outwords[14];
-  Put224Bits(outwords, x);
-  Put224Bits(outwords + 7, y);
-  return std::string(reinterpret_cast<const char*>(outwords), sizeof(outwords));
-}
-
-void ScalarMult(const Point& in, const uint8* scalar, Point* out) {
-  ::ScalarMult(out, in, scalar, 28);
-}
-
-// kBasePoint is the base point (generator) of the elliptic curve group.
-static const Point kBasePoint = {
-  {22813985, 52956513, 34677300, 203240812,
-   12143107, 133374265, 225162431, 191946955},
-  {83918388, 223877528, 122119236, 123340192,
-   266784067, 263504429, 146143011, 198407736},
-  {1, 0, 0, 0, 0, 0, 0, 0},
-};
-
-void ScalarBaseMult(const uint8* scalar, Point* out) {
-  ::ScalarMult(out, kBasePoint, scalar, 28);
-}
-
-void Add(const Point& a, const Point& b, Point* out) {
-  AddJacobian(out, a, b);
-}
-
-void Negate(const Point& in, Point* out) {
-  // Guide to elliptic curve cryptography, page 89 suggests that (X : X+Y : Z)
-  // is the negative in Jacobian coordinates, but it doesn't actually appear to
-  // be true in testing so this performs the negation in affine coordinates.
-  FieldElement zinv, zinv_sq, y;
-  Invert(&zinv, in.z);
-  Square(&zinv_sq, zinv);
-  Mul(&out->x, in.x, zinv_sq);
-  Mul(&zinv_sq, zinv_sq, zinv);
-  Mul(&y, in.y, zinv_sq);
-
-  Subtract(&out->y, kP, y);
-  Reduce(&out->y);
-
-  memset(&out->z, 0, sizeof(out->z));
-  out->z[0] = 1;
-}
-
-}  // namespace p224
-
-}  // namespace crypto