# < Summary

Information

Class: | Renci.SshNet.Security.Org.BouncyCastle.Math.EC.Multiplier.FixedPointCombMultiplier
Assembly: | Renci.SshNet
File(s): | \home\appveyor\projects\ssh-net\src\Renci.SshNet\Security\BouncyCastle\math\ec\multiplier\FixedPointCombMultiplier.cs

Line coverage
93%

Covered lines: | 27
Uncovered lines: | 2
Coverable lines: | 29
Total lines: | 58
Line coverage: | 93.1%

Branch coverage
83%

Covered branches: | 5
Total branches: | 6
Branch coverage: | 83.3%

Method coverage

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# Metrics

Method | Branch coverage | Cyclomatic complexity | Line coverage
--- | --- | --- | ---
MultiplyPositive(...) | 83.33% | 6 | 93.1%

# File(s)

## \home\appveyor\projects\ssh-net\src\Renci.SshNet\Security\BouncyCastle\math\ec\multiplier\FixedPointCombMultiplier.cs

| # | Line |  | Line coverage
--- | --- | --- | --- | ---
|  | `1` |  | `using System;`
|  | `2` |  | ``
|  | `3` |  | `using Renci.SshNet.Security.Org.BouncyCastle.Math.Raw;`
|  | `4` |  | ``
|  | `5` |  | `namespace Renci.SshNet.Security.Org.BouncyCastle.Math.EC.Multiplier`
|  | `6` |  | `{`
|  | `7` |  | `internal class FixedPointCombMultiplier`
|  | `8` |  | `: AbstractECMultiplier`
|  | `9` |  | `{`
|  | `10` |  | `protected override ECPoint MultiplyPositive(ECPoint p, BigInteger k)`
| 9 | `11` |  | `{`
| 9 | `12` |  | `ECCurve c = p.Curve;`
| 9 | `13` |  | `int size = FixedPointUtilities.GetCombSize(c);`
|  | `14` |  | ``
| 9 | `15` |  | `if (k.BitLength > size)`
| 0 | `16` |  | `{`
|  | `17` |  | `/*`
|  | `18` |  | `* TODO The comb works best when the scalars are less than the (possibly unknown) order.`
|  | `19` |  | `* Still, if we want to handle larger scalars, we could allow customization of the comb`
|  | `20` |  | `* size, or alternatively we could deal with the 'extra' bits either by running the comb`
|  | `21` |  | `* multiple times as necessary, or by using an alternative multiplier as prelude.`
|  | `22` |  | `*/`
| 0 | `23` |  | `throw new InvalidOperationException("fixed-point comb doesn't support scalars larger than the curve orde`
|  | `24` |  | `}`
|  | `25` |  | ``
| 9 | `26` |  | `FixedPointPreCompInfo info = FixedPointUtilities.Precompute(p);`
| 9 | `27` |  | `ECLookupTable lookupTable = info.LookupTable;`
| 9 | `28` |  | `int width = info.Width;`
|  | `29` |  | ``
| 9 | `30` |  | `int d = (size + width - 1) / width;`
|  | `31` |  | ``
| 9 | `32` |  | `ECPoint R = c.Infinity;`
|  | `33` |  | ``
| 9 | `34` |  | `int fullComb = d * width;`
| 9 | `35` |  | `uint[] K = Nat.FromBigInteger(fullComb, k);`
|  | `36` |  | ``
| 9 | `37` |  | `int top = fullComb - 1;`
| 1182 | `38` |  | `for (int i = 0; i < d; ++i)`
| 582 | `39` |  | `{`
| 582 | `40` |  | `uint secretIndex = 0;`
|  | `41` |  | ``
| 8148 | `42` |  | `for (int j = top - i; j >= 0; j -= d)`
| 3492 | `43` |  | `{`
| 3492 | `44` |  | `uint secretBit = K[j >> 5] >> (j & 0x1F);`
| 3492 | `45` |  | `secretIndex ^= secretBit >> 1;`
| 3492 | `46` |  | `secretIndex <<= 1;`
| 3492 | `47` |  | `secretIndex ^= secretBit;`
| 3492 | `48` |  | `}`
|  | `49` |  | ``
| 582 | `50` |  | `ECPoint add = lookupTable.Lookup((int)secretIndex);`
|  | `51` |  | ``
| 582 | `52` |  | `R = R.TwicePlus(add);`
| 582 | `53` |  | `}`
|  | `54` |  | ``
| 9 | `55` |  | `return R.Add(info.Offset);`
| 9 | `56` |  | `}`
|  | `57` |  | `}`
|  | `58` |  | `}`

# Methods/Properties

MultiplyPositive(Renci.SshNet.Security.Org.BouncyCastle.Math.EC.ECPoint,Renci.SshNet.Security.Org.BouncyCastle.Math.BigInteger)