diff --git a/docs/project/list-of-diagnostics.md b/docs/project/list-of-diagnostics.md
index 9497fc7b692d18..2d168532317584 100644
--- a/docs/project/list-of-diagnostics.md
+++ b/docs/project/list-of-diagnostics.md
@@ -83,6 +83,8 @@ The PR that reveals the implementation of the `<IncludeInternalObsoleteAttribute
 |  __`SYSLIB0026`__ | X509Certificate and X509Certificate2 are immutable. Use the appropriate constructor to create a new certificate. |
 |  __`SYSLIB0027`__ | PublicKey.Key is obsolete. Use the appropriate method to get the public key, such as GetRSAPublicKey. |
 |  __`SYSLIB0028`__ | X509Certificate2.PrivateKey is obsolete. Use the appropriate method to get the private key, such as GetRSAPrivateKey, or use the CopyWithPrivateKey method to create a new instance with a private key. |
+|  __`SYSLIB0029`__ | ProduceLegacyHmacValues is obsolete. Producing legacy HMAC values is no longer supported. |
+|  __`SYSLIB0030`__ | HMACSHA1 always uses the algorithm implementation provided by the platform. Use a constructor without the useManagedSha1 parameter. |
 
 ## Analyzer Warnings
 
diff --git a/src/libraries/Common/src/System/Obsoletions.cs b/src/libraries/Common/src/System/Obsoletions.cs
index 71223c530001d2..613d51a5ba7833 100644
--- a/src/libraries/Common/src/System/Obsoletions.cs
+++ b/src/libraries/Common/src/System/Obsoletions.cs
@@ -95,5 +95,11 @@ internal static class Obsoletions
 
         internal const string X509CertificatePrivateKeyMessage = "X509Certificate2.PrivateKey is obsolete. Use the appropriate method to get the private key, such as GetRSAPrivateKey, or use the CopyWithPrivateKey method to create a new instance with a private key.";
         internal const string X509CertificatePrivateKeyDiagId = "SYSLIB0028";
+
+        internal const string ProduceLegacyHmacValuesMessage = "ProduceLegacyHmacValues is obsolete. Producing legacy HMAC values is no longer supported.";
+        internal const string ProduceLegacyHmacValuesDiagId = "SYSLIB0029";
+
+        internal const string UseManagedSha1Message = "HMACSHA1 always uses the algorithm implementation provided by the platform. Use a constructor without the useManagedSha1 parameter.";
+        internal const string UseManagedSha1DiagId = "SYSLIB0030";
     }
 }
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs b/src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs
index 323966899bc0ac..cbe93e981f360c 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs
@@ -483,6 +483,7 @@ public partial class HMACSHA1 : System.Security.Cryptography.HMAC
         public HMACSHA1() { }
         public HMACSHA1(byte[] key) { }
         [System.ComponentModel.EditorBrowsableAttribute(System.ComponentModel.EditorBrowsableState.Never)]
+        [System.ObsoleteAttribute("HMACSHA1 always uses the algorithm implementation provided by the platform. Use a constructor without the useManagedSha1 parameter.", DiagnosticId = "SYSLIB0030", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public HMACSHA1(byte[] key, bool useManagedSha1) { }
         public override byte[] Key { get { throw null; } set { } }
         protected override void Dispose(bool disposing) { }
@@ -519,6 +520,7 @@ public partial class HMACSHA384 : System.Security.Cryptography.HMAC
         public HMACSHA384() { }
         public HMACSHA384(byte[] key) { }
         public override byte[] Key { get { throw null; } set { } }
+        [System.ObsoleteAttribute("ProduceLegacyHmacValues is obsolete. Producing legacy HMAC values is no longer supported.", DiagnosticId = "SYSLIB0029", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public bool ProduceLegacyHmacValues { get { throw null; } set { } }
         protected override void Dispose(bool disposing) { }
         protected override void HashCore(byte[] rgb, int ib, int cb) { }
@@ -537,6 +539,7 @@ public partial class HMACSHA512 : System.Security.Cryptography.HMAC
         public HMACSHA512() { }
         public HMACSHA512(byte[] key) { }
         public override byte[] Key { get { throw null; } set { } }
+        [System.ObsoleteAttribute("ProduceLegacyHmacValues is obsolete. Producing legacy HMAC values is no longer supported.", DiagnosticId = "SYSLIB0029", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public bool ProduceLegacyHmacValues { get { throw null; } set { } }
         protected override void Dispose(bool disposing) { }
         protected override void HashCore(byte[] rgb, int ib, int cb) { }
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA1.cs b/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA1.cs
index 39e57c3fe72199..424cec12e8313a 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA1.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA1.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Internal.Cryptography;
+using System;
 using System.ComponentModel;
 using System.Diagnostics;
 using System.Runtime.Versioning;
@@ -42,6 +43,7 @@ public HMACSHA1(byte[] key)
         }
 
         [EditorBrowsable(EditorBrowsableState.Never)]
+        [Obsolete(Obsoletions.UseManagedSha1Message, DiagnosticId = Obsoletions.UseManagedSha1DiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public HMACSHA1(byte[] key, bool useManagedSha1) : this(key)
         {
             // useManagedSha1 is ignored
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA384.cs b/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA384.cs
index bf167162e4c0af..b5b5ea33a9e995 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA384.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA384.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Internal.Cryptography;
+using System;
 using System.Diagnostics;
 using System.Runtime.Versioning;
 using System.Security.Cryptography;
@@ -40,6 +41,7 @@ public HMACSHA384(byte[] key)
             Debug.Assert(HashSizeValue == HmacSizeBits);
         }
 
+        [Obsolete(Obsoletions.ProduceLegacyHmacValuesMessage, DiagnosticId = Obsoletions.ProduceLegacyHmacValuesDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public bool ProduceLegacyHmacValues
         {
             get
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA512.cs b/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA512.cs
index 9b25cdca959a74..dc1ea8d688b717 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA512.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/HMACSHA512.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Internal.Cryptography;
+using System;
 using System.Diagnostics;
 using System.Runtime.Versioning;
 using System.Security.Cryptography;
@@ -39,6 +40,7 @@ public HMACSHA512(byte[] key)
             HashSizeValue = _hMacCommon.HashSizeInBits;
         }
 
+        [Obsolete(Obsoletions.ProduceLegacyHmacValuesMessage, DiagnosticId = Obsoletions.ProduceLegacyHmacValuesDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
         public bool ProduceLegacyHmacValues
         {
             get
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha1Tests.cs b/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha1Tests.cs
index 49a9d6de1bb03a..83dbf48b1baa24 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha1Tests.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha1Tests.cs
@@ -64,16 +64,18 @@ public void HmacSha1_Byte_Constructors()
             using (HMACSHA1 h1 = new HMACSHA1(key))
             {
                 VerifyHmac_KeyAlreadySet(h1, 1, digest);
-                using (HMACSHA1 h2 = new HMACSHA1(key, true))
+#pragma warning disable SYSLIB0030 // useManagedSha1 is obsolete
+                using (HMACSHA1 h2 = new HMACSHA1(key, useManagedSha1: true))
                 {
                     VerifyHmac_KeyAlreadySet(h2, 1, digest);
                     Assert.Equal(h1.Key, h2.Key);
                 }
-                using (HMACSHA1 h2 = new HMACSHA1(key, false))
+                using (HMACSHA1 h2 = new HMACSHA1(key, useManagedSha1: false))
                 {
                     VerifyHmac_KeyAlreadySet(h1, 1, digest);
                     Assert.Equal(h1.Key, h2.Key);
                 }
+#pragma warning restore SYSLIB0030
             }
         }
 
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha384Tests.cs b/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha384Tests.cs
index 76325f1ba65545..53d0dece6d3b98 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha384Tests.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha384Tests.cs
@@ -48,9 +48,11 @@ public void ProduceLegacyHmacValues()
         {
             using (var h = new HMACSHA384())
             {
+#pragma warning disable SYSLIB0029 // ProduceLegacyHmacValues is obsolete
                 Assert.False(h.ProduceLegacyHmacValues);
                 h.ProduceLegacyHmacValues = false; // doesn't throw
                 Assert.Throws<PlatformNotSupportedException>(() => h.ProduceLegacyHmacValues = true);
+#pragma warning restore SYSLIB0029
             }
         }
 
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha512Tests.cs b/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha512Tests.cs
index 4da18847fd993e..c9f52a982c0ddd 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha512Tests.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/tests/HmacSha512Tests.cs
@@ -48,9 +48,11 @@ public void ProduceLegacyHmacValues()
         {
             using (var h = new HMACSHA512())
             {
+#pragma warning disable SYSLIB0029 // ProduceLegacyHmacValues is obsolete
                 Assert.False(h.ProduceLegacyHmacValues);
                 h.ProduceLegacyHmacValues = false; // doesn't throw
                 Assert.Throws<PlatformNotSupportedException>(() => h.ProduceLegacyHmacValues = true);
+#pragma warning restore SYSLIB0029
             }
         }