# < Summary

Information

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

Line coverage
92%

Covered lines: | 26
Uncovered lines: | 2
Coverable lines: | 28
Total lines: | 90
Line coverage: | 92.8%

Branch coverage
50%

Covered branches: | 1
Total branches: | 2
Branch coverage: | 50%

Method coverage

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# Metrics

Method | Branch coverage | Cyclomatic complexity | Line coverage
--- | --- | --- | ---
.ctor(...) | 50% | 2 | 75%
Verify(...) | 100% | 1 | 100%
Sign(...) | 100% | 1 | 100%
DerEncode(...) | 100% | 1 | 100%

# File(s)

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

| # | Line |  | Line coverage
--- | --- | --- | --- | ---
|  | `1` |  | `using System;`
|  | `2` |  | `using Renci.SshNet.Common;`
|  | `3` |  | ``
|  | `4` |  | `namespace Renci.SshNet.Security.Cryptography`
|  | `5` |  | `{`
|  | `6` |  | `/// <summary>`
|  | `7` |  | `/// Implements digital signature where where asymmetric cipher is used.`
|  | `8` |  | `/// </summary>`
|  | `9` |  | `public abstract class CipherDigitalSignature : DigitalSignature`
|  | `10` |  | `{`
|  | `11` |  | `private readonly AsymmetricCipher _cipher;`
|  | `12` |  | `private readonly ObjectIdentifier _oid;`
|  | `13` |  | ``
|  | `14` |  | `/// <summary>`
|  | `15` |  | `/// Initializes a new instance of the <see cref="CipherDigitalSignature"/> class.`
|  | `16` |  | `/// </summary>`
|  | `17` |  | `/// <param name="oid">The object identifier.</param>`
|  | `18` |  | `/// <param name="cipher">The cipher.</param>`
| 2768 | `19` |  | `protected CipherDigitalSignature(ObjectIdentifier oid, AsymmetricCipher cipher)`
| 2768 | `20` |  | `{`
| 2768 | `21` |  | `if (cipher is null)`
| 0 | `22` |  | `{`
| 0 | `23` |  | `throw new ArgumentNullException(nameof(cipher));`
|  | `24` |  | `}`
|  | `25` |  | ``
| 2768 | `26` |  | `_cipher = cipher;`
| 2768 | `27` |  | `_oid = oid;`
| 2768 | `28` |  | `}`
|  | `29` |  | ``
|  | `30` |  | `/// <summary>`
|  | `31` |  | `/// Verifies the signature.`
|  | `32` |  | `/// </summary>`
|  | `33` |  | `/// <param name="input">The input.</param>`
|  | `34` |  | `/// <param name="signature">The signature.</param>`
|  | `35` |  | `/// <returns>`
|  | `36` |  | `/// <see langword="true"/> if signature was successfully verified; otherwise <see langword="false"/>.`
|  | `37` |  | `/// </returns>`
|  | `38` |  | `public override bool Verify(byte[] input, byte[] signature)`
| 1210 | `39` |  | `{`
| 1210 | `40` |  | `var encryptedSignature = _cipher.Decrypt(signature);`
| 1210 | `41` |  | `var hashData = Hash(input);`
| 1210 | `42` |  | `var expected = DerEncode(hashData);`
| 1210 | `43` |  | `return expected.IsEqualTo(encryptedSignature);`
| 1210 | `44` |  | `}`
|  | `45` |  | ``
|  | `46` |  | `/// <summary>`
|  | `47` |  | `/// Creates the signature.`
|  | `48` |  | `/// </summary>`
|  | `49` |  | `/// <param name="input">The input.</param>`
|  | `50` |  | `/// <returns>`
|  | `51` |  | `/// Signed input data.`
|  | `52` |  | `/// </returns>`
|  | `53` |  | `public override byte[] Sign(byte[] input)`
| 696 | `54` |  | `{`
|  | `55` |  | `// Calculate hash value`
| 696 | `56` |  | `var hashData = Hash(input);`
|  | `57` |  | ``
|  | `58` |  | `// Calculate DER string`
| 696 | `59` |  | `var derEncodedHash = DerEncode(hashData);`
|  | `60` |  | ``
| 696 | `61` |  | `return _cipher.Encrypt(derEncodedHash).TrimLeadingZeros();`
| 696 | `62` |  | `}`
|  | `63` |  | ``
|  | `64` |  | `/// <summary>`
|  | `65` |  | `/// Hashes the specified input.`
|  | `66` |  | `/// </summary>`
|  | `67` |  | `/// <param name="input">The input.</param>`
|  | `68` |  | `/// <returns>Hashed data.</returns>`
|  | `69` |  | `protected abstract byte[] Hash(byte[] input);`
|  | `70` |  | ``
|  | `71` |  | `/// <summary>`
|  | `72` |  | `/// Encodes hash using DER.`
|  | `73` |  | `/// </summary>`
|  | `74` |  | `/// <param name="hashData">The hash data.</param>`
|  | `75` |  | `/// <returns>`
|  | `76` |  | `/// DER Encoded byte array.`
|  | `77` |  | `/// </returns>`
|  | `78` |  | `protected byte[] DerEncode(byte[] hashData)`
| 1906 | `79` |  | `{`
| 1906 | `80` |  | `var alg = new DerData();`
| 1906 | `81` |  | `alg.Write(_oid);`
| 1906 | `82` |  | `alg.WriteNull();`
|  | `83` |  | ``
| 1906 | `84` |  | `var data = new DerData();`
| 1906 | `85` |  | `data.Write(alg);`
| 1906 | `86` |  | `data.Write(hashData);`
| 1906 | `87` |  | `return data.Encode();`
| 1906 | `88` |  | `}`
|  | `89` |  | `}`
|  | `90` |  | `}`

# Methods/Properties

.ctor(Renci.SshNet.Common.ObjectIdentifier,Renci.SshNet.Security.Cryptography.AsymmetricCipher)
Verify(System.Byte[],System.Byte[])
Sign(System.Byte[])
DerEncode(System.Byte[])