CA5384: Do not use digital signature algorithm (DSA)

Article
11/14/2023

Property	Value
Rule ID	CA5384
Title	Do not use digital signature algorithm (DSA)
Category	Security
Fix is breaking or non-breaking	Non-breaking
Enabled by default in .NET 9	No

Cause

Using DSA in one of the following ways:

Returning or instantiating derived classes of System.Security.Cryptography.DSA
Using System.Security.Cryptography.AsymmetricAlgorithm.Create or System.Security.Cryptography.CryptoConfig.CreateFromName to create a DSA object.

By default, this rule analyzes the entire codebase, but this is configurable.

Rule description

DSA is a weak asymmetric encryption algorithm.

How to fix violations

Switch to an RSA with at least 2048 key size, ECDH or ECDsa algorithm instead.

When to suppress warnings

It is not recommended to suppress this rule unless for compatibility with legacy applications and data.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable CA5384
// The code that's violating the rule is on this line.
#pragma warning restore CA5384

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

[*.{cs,vb}]
dotnet_diagnostic.CA5384.severity = none

For more information, see How to suppress code analysis warnings.

Configure code to analyze

Use the following options to configure which parts of your codebase to run this rule on.

Exclude specific symbols
Exclude specific types and their derived types

You can configure these options for just this rule, for all rules it applies to, or for all rules in this category (Security) that it applies to. For more information, see Code quality rule configuration options.

Exclude specific symbols

You can exclude specific symbols, such as types and methods, from analysis. For example, to specify that the rule should not run on any code within types named MyType, add the following key-value pair to an .editorconfig file in your project:

dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType

Allowed symbol name formats in the option value (separated by |):

Symbol name only (includes all symbols with the name, regardless of the containing type or namespace).
Fully qualified names in the symbol's documentation ID format. Each symbol name requires a symbol-kind prefix, such as M: for methods, T: for types, and N: for namespaces.
.ctor for constructors and .cctor for static constructors.

Examples:

Option Value	Summary
`dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType`	Matches all symbols named `MyType`.
`dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType1\|MyType2`	Matches all symbols named either `MyType1` or `MyType2`.
`dotnet_code_quality.CAXXXX.excluded_symbol_names = M:NS.MyType.MyMethod(ParamType)`	Matches specific method `MyMethod` with the specified fully qualified signature.
`dotnet_code_quality.CAXXXX.excluded_symbol_names = M:NS1.MyType1.MyMethod1(ParamType)\|M:NS2.MyType2.MyMethod2(ParamType)`	Matches specific methods `MyMethod1` and `MyMethod2` with the respective fully qualified signatures.

Exclude specific types and their derived types

You can exclude specific types and their derived types from analysis. For example, to specify that the rule should not run on any methods within types named MyType and their derived types, add the following key-value pair to an .editorconfig file in your project:

dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType

Allowed symbol name formats in the option value (separated by |):

Type name only (includes all types with the name, regardless of the containing type or namespace).
Fully qualified names in the symbol's documentation ID format, with an optional T: prefix.

Examples:

Option Value	Summary
`dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType`	Matches all types named `MyType` and all of their derived types.
`dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType1\|MyType2`	Matches all types named either `MyType1` or `MyType2` and all of their derived types.
`dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = M:NS.MyType`	Matches specific type `MyType` with given fully qualified name and all of its derived types.
`dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = M:NS1.MyType1\|M:NS2.MyType2`	Matches specific types `MyType1` and `MyType2` with the respective fully qualified names, and all of their derived types.

Example

The following code snippet illustrates the pattern detected by this rule.

Violation:

using System.Security.Cryptography;

class ExampleClass
{
    public void ExampleMethod()
    {
        DSACng dsaCng = new DSACng();
    }
}

Solution:

using System.Security.Cryptography;

class ExampleClass
{
    public void ExampleMethod()
    {
        AsymmetricAlgorithm asymmetricAlgorithm = AsymmetricAlgorithm.Create("ECDsa");
    }
}

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