<Target Name="ChangeAliasesOfStrongNameAssemblies" BeforeTargets="FindReferenceAssembliesForReferences;ResolveReferences">
    <ItemGroup>
      <ReferencePath Condition="'%(FileName)' == 'abc'">
        <Aliases>def</Aliases>
      </ReferencePath>
    </ItemGroup>
  </Target>

extern alias efg;

using efg::AssemblyNameSpace;

...