# < Summary

Information

Class: | Renci.SshNet.Security.Cryptography.Ciphers.Arc4Cipher
Assembly: | Renci.SshNet
File(s): | \home\appveyor\projects\ssh-net\src\Renci.SshNet\Security\Cryptography\Ciphers\Arc4Cipher.cs

Line coverage
77%

Covered lines: | 49
Uncovered lines: | 14
Coverable lines: | 63
Total lines: | 184
Line coverage: | 77.7%

Branch coverage
78%

Covered branches: | 11
Total branches: | 14
Branch coverage: | 78.5%

Method coverage

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# Metrics

Method | Branch coverage | Cyclomatic complexity | Line coverage
--- | --- | --- | ---
get_MinimumSize() | 100% | 1 | 0%
.ctor(...) | 50% | 2 | 62.5%
EncryptBlock(...) | 100% | 1 | 0%
DecryptBlock(...) | 100% | 1 | 0%
Encrypt(...) | 100% | 1 | 100%
Decrypt(...) | 100% | 1 | 100%
Decrypt(...) | 100% | 1 | 100%
ProcessBytes(...) | 66.66% | 6 | 77.77%
SetKey(...) | 100% | 6 | 100%

# File(s)

## \home\appveyor\projects\ssh-net\src\Renci.SshNet\Security\Cryptography\Ciphers\Arc4Cipher.cs

| # | Line |  | Line coverage
--- | --- | --- | --- | ---
|  | `1` |  | `using System;`
|  | `2` |  | ``
|  | `3` |  | `namespace Renci.SshNet.Security.Cryptography.Ciphers`
|  | `4` |  | `{`
|  | `5` |  | `/// <summary>`
|  | `6` |  | `/// Implements ARCH4 cipher algorithm.`
|  | `7` |  | `/// </summary>`
|  | `8` |  | `public sealed class Arc4Cipher : StreamCipher`
|  | `9` |  | `{`
|  | `10` |  | `#pragma warning disable SA1310 // Field names should not contain underscore`
|  | `11` |  | `private const int STATE_LENGTH = 256;`
|  | `12` |  | `#pragma warning restore SA1310 // Field names should not contain underscore`
|  | `13` |  | ``
|  | `14` |  | `/// <summary>`
|  | `15` |  | `/// Holds the state of the RC4 engine.`
|  | `16` |  | `/// </summary>`
|  | `17` |  | `private byte[] _engineState;`
|  | `18` |  | ``
|  | `19` |  | `private int _x;`
|  | `20` |  | ``
|  | `21` |  | `private int _y;`
|  | `22` |  | ``
|  | `23` |  | `/// <summary>`
|  | `24` |  | `/// Gets the minimum data size.`
|  | `25` |  | `/// </summary>`
|  | `26` |  | `/// <value>`
|  | `27` |  | `/// The minimum data size.`
|  | `28` |  | `/// </value>`
|  | `29` |  | `public override byte MinimumSize`
|  | `30` |  | `{`
| 0 | `31` |  | `get { return 0; }`
|  | `32` |  | `}`
|  | `33` |  | ``
|  | `34` |  | `/// <summary>`
|  | `35` |  | `/// Initializes a new instance of the <see cref="Arc4Cipher" /> class.`
|  | `36` |  | `/// </summary>`
|  | `37` |  | `/// <param name="key">The key.</param>`
|  | `38` |  | `/// <param name="dischargeFirstBytes">if set to <see langword="true"/> will disharged first 1536 bytes.</param>`
|  | `39` |  | `/// <exception cref="ArgumentNullException"><paramref name="key" /> is <see langword="null"/>.</exception>`
|  | `40` |  | `public Arc4Cipher(byte[] key, bool dischargeFirstBytes)`
| 18 | `41` |  | `: base(key)`
| 18 | `42` |  | `{`
| 18 | `43` |  | `SetKey(key);`
|  | `44` |  | ``
|  | `45` |  | `// The first 1536 bytes of keystream generated by the cipher MUST be discarded, and the first byte of the`
|  | `46` |  | `// first encrypted packet MUST be encrypted using the 1537th byte of keystream.`
| 18 | `47` |  | `if (dischargeFirstBytes)`
| 0 | `48` |  | `{`
| 0 | `49` |  | `_ = Encrypt(new byte[1536]);`
| 0 | `50` |  | `}`
| 18 | `51` |  | `}`
|  | `52` |  | ``
|  | `53` |  | `/// <summary>`
|  | `54` |  | `/// Encrypts the specified region of the input byte array and copies the encrypted data to the specified region`
|  | `55` |  | `/// </summary>`
|  | `56` |  | `/// <param name="inputBuffer">The input data to encrypt.</param>`
|  | `57` |  | `/// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>`
|  | `58` |  | `/// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>`
|  | `59` |  | `/// <param name="outputBuffer">The output to which to write encrypted data.</param>`
|  | `60` |  | `/// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>`
|  | `61` |  | `/// <returns>`
|  | `62` |  | `/// The number of bytes encrypted.`
|  | `63` |  | `/// </returns>`
|  | `64` |  | `public override int EncryptBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int o`
| 0 | `65` |  | `{`
| 0 | `66` |  | `return ProcessBytes(inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);`
| 0 | `67` |  | `}`
|  | `68` |  | ``
|  | `69` |  | `/// <summary>`
|  | `70` |  | `/// Decrypts the specified region of the input byte array and copies the decrypted data to the specified region`
|  | `71` |  | `/// </summary>`
|  | `72` |  | `/// <param name="inputBuffer">The input data to decrypt.</param>`
|  | `73` |  | `/// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>`
|  | `74` |  | `/// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>`
|  | `75` |  | `/// <param name="outputBuffer">The output to which to write decrypted data.</param>`
|  | `76` |  | `/// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>`
|  | `77` |  | `/// <returns>`
|  | `78` |  | `/// The number of bytes decrypted.`
|  | `79` |  | `/// </returns>`
|  | `80` |  | `public override int DecryptBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int o`
| 0 | `81` |  | `{`
| 0 | `82` |  | `return ProcessBytes(inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);`
| 0 | `83` |  | `}`
|  | `84` |  | ``
|  | `85` |  | `/// <summary>`
|  | `86` |  | `/// Encrypts the specified input.`
|  | `87` |  | `/// </summary>`
|  | `88` |  | `/// <param name="input">The input.</param>`
|  | `89` |  | `/// <param name="offset">The zero-based offset in <paramref name="input"/> at which to begin encrypting.</param>`
|  | `90` |  | `/// <param name="length">The number of bytes to encrypt from <paramref name="input"/>.</param>`
|  | `91` |  | `/// <returns>`
|  | `92` |  | `/// Encrypted data.`
|  | `93` |  | `/// </returns>`
|  | `94` |  | `public override byte[] Encrypt(byte[] input, int offset, int length)`
| 18 | `95` |  | `{`
| 18 | `96` |  | `var output = new byte[length];`
| 18 | `97` |  | `_ = ProcessBytes(input, offset, length, output, 0);`
| 18 | `98` |  | `return output;`
| 18 | `99` |  | `}`
|  | `100` |  | ``
|  | `101` |  | `/// <summary>`
|  | `102` |  | `/// Decrypts the specified input.`
|  | `103` |  | `/// </summary>`
|  | `104` |  | `/// <param name="input">The input.</param>`
|  | `105` |  | `/// <returns>`
|  | `106` |  | `/// The decrypted data.`
|  | `107` |  | `/// </returns>`
|  | `108` |  | `public override byte[] Decrypt(byte[] input)`
| 6 | `109` |  | `{`
| 6 | `110` |  | `return Decrypt(input, 0, input.Length);`
| 6 | `111` |  | `}`
|  | `112` |  | ``
|  | `113` |  | `/// <summary>`
|  | `114` |  | `/// Decrypts the specified input.`
|  | `115` |  | `/// </summary>`
|  | `116` |  | `/// <param name="input">The input.</param>`
|  | `117` |  | `/// <param name="offset">The zero-based offset in <paramref name="input"/> at which to begin decrypting.</param>`
|  | `118` |  | `/// <param name="length">The number of bytes to decrypt from <paramref name="input"/>.</param>`
|  | `119` |  | `/// <returns>`
|  | `120` |  | `/// The decrypted data.`
|  | `121` |  | `/// </returns>`
|  | `122` |  | `public override byte[] Decrypt(byte[] input, int offset, int length)`
| 9 | `123` |  | `{`
| 9 | `124` |  | `return Encrypt(input, offset, length);`
| 9 | `125` |  | `}`
|  | `126` |  | ``
|  | `127` |  | `private int ProcessBytes(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOff`
| 18 | `128` |  | `{`
| 18 | `129` |  | `if ((inputOffset + inputCount) > inputBuffer.Length)`
| 0 | `130` |  | `{`
| 0 | `131` |  | `throw new ArgumentException("input buffer too short");`
|  | `132` |  | `}`
|  | `133` |  | ``
| 18 | `134` |  | `if ((outputOffset + inputCount) > outputBuffer.Length)`
| 0 | `135` |  | `{`
| 0 | `136` |  | `throw new ArgumentException("output buffer too short");`
|  | `137` |  | `}`
|  | `138` |  | ``
| 288 | `139` |  | `for (var i = 0; i < inputCount; i++)`
| 126 | `140` |  | `{`
| 126 | `141` |  | `_x = (_x + 1) & 0xff;`
| 126 | `142` |  | `_y = (_engineState[_x] + _y) & 0xff;`
|  | `143` |  | ``
|  | `144` |  | `// swap`
| 126 | `145` |  | `var tmp = _engineState[_x];`
| 126 | `146` |  | `_engineState[_x] = _engineState[_y];`
| 126 | `147` |  | `_engineState[_y] = tmp;`
|  | `148` |  | ``
|  | `149` |  | `// xor`
| 126 | `150` |  | `outputBuffer[i + outputOffset] = (byte)(inputBuffer[i + inputOffset] ^ _engineState[(_engineState[_x] +`
| 126 | `151` |  | `}`
|  | `152` |  | ``
| 18 | `153` |  | `return inputCount;`
| 18 | `154` |  | `}`
|  | `155` |  | ``
|  | `156` |  | `private void SetKey(byte[] keyBytes)`
| 18 | `157` |  | `{`
| 18 | `158` |  | `_x = 0;`
| 18 | `159` |  | `_y = 0;`
|  | `160` |  | ``
| 18 | `161` |  | `_engineState ??= new byte[STATE_LENGTH];`
|  | `162` |  | ``
|  | `163` |  | `// reset the state of the engine`
| 9252 | `164` |  | `for (var i = 0; i < STATE_LENGTH; i++)`
| 4608 | `165` |  | `{`
| 4608 | `166` |  | `_engineState[i] = (byte) i;`
| 4608 | `167` |  | `}`
|  | `168` |  | ``
| 18 | `169` |  | `var i1 = 0;`
| 18 | `170` |  | `var i2 = 0;`
|  | `171` |  | ``
| 9252 | `172` |  | `for (var i = 0; i < STATE_LENGTH; i++)`
| 4608 | `173` |  | `{`
| 4608 | `174` |  | `i2 = ((keyBytes[i1] & 0xff) + _engineState[i] + i2) & 0xff;`
|  | `175` |  | ``
|  | `176` |  | `// do the byte-swap inline`
| 4608 | `177` |  | `var tmp = _engineState[i];`
| 4608 | `178` |  | `_engineState[i] = _engineState[i2];`
| 4608 | `179` |  | `_engineState[i2] = tmp;`
| 4608 | `180` |  | `i1 = (i1 + 1) % keyBytes.Length;`
| 4608 | `181` |  | `}`
| 18 | `182` |  | `}`
|  | `183` |  | `}`
|  | `184` |  | `}`

# Methods/Properties

get_MinimumSize()
.ctor(System.Byte[],System.Boolean)
EncryptBlock(System.Byte[],System.Int32,System.Int32,System.Byte[],System.Int32)
DecryptBlock(System.Byte[],System.Int32,System.Int32,System.Byte[],System.Int32)
Encrypt(System.Byte[],System.Int32,System.Int32)
Decrypt(System.Byte[])
Decrypt(System.Byte[],System.Int32,System.Int32)
ProcessBytes(System.Byte[],System.Int32,System.Int32,System.Byte[],System.Int32)
SetKey(System.Byte[])