diff --git a/app/src/main/java/org/matrix/TEESimulator/attestation/AttestationConstants.kt b/app/src/main/java/org/matrix/TEESimulator/attestation/AttestationConstants.kt
index 767e8b3..a899a12 100644
--- a/app/src/main/java/org/matrix/TEESimulator/attestation/AttestationConstants.kt
+++ b/app/src/main/java/org/matrix/TEESimulator/attestation/AttestationConstants.kt
@@ -89,5 +89,5 @@ object AttestationConstants {
 
     // --- Other Constants ---
     // https://cs.android.com/android/platform/superproject/main/+/main:system/keymaster/km_openssl/attestation_record.cpp
-    const val CHALLENGE_LENGTH_LIMIT = 128 // kMaximumAttestationChallengeLength
+    const val CHALLENGE_LENGTH_LIMIT = 128
 }
diff --git a/app/src/main/java/org/matrix/TEESimulator/interception/keystore/Keystore2Interceptor.kt b/app/src/main/java/org/matrix/TEESimulator/interception/keystore/Keystore2Interceptor.kt
index 64145d6..8d25fb3 100644
--- a/app/src/main/java/org/matrix/TEESimulator/interception/keystore/Keystore2Interceptor.kt
+++ b/app/src/main/java/org/matrix/TEESimulator/interception/keystore/Keystore2Interceptor.kt
@@ -10,6 +10,7 @@ import android.system.keystore2.KeyDescriptor
 import android.system.keystore2.KeyEntryResponse
 import java.security.SecureRandom
 import java.security.cert.Certificate
+import java.util.concurrent.ConcurrentHashMap
 import org.matrix.TEESimulator.attestation.AttestationPatcher
 import org.matrix.TEESimulator.attestation.KeyMintAttestation
 import org.matrix.TEESimulator.config.ConfigurationManager
@@ -54,6 +55,9 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
             .associate { field -> (field.get(null) as Int) to field.name.split("_")[1] }
     }
 
+    private const val RESPONSE_KEY_NOT_FOUND = 7
+    private val deletedSoftwareKeys: MutableSet<KeyIdentifier> = ConcurrentHashMap.newKeySet()
+
     override val serviceName = "android.system.keystore2.IKeystoreService/default"
     override val processName = "keystore2"
     override val injectionCommand = "exec ./inject `pidof keystore2` libTEESimulator.so entry"
@@ -156,8 +160,10 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
             val keyId = KeyIdentifier(callingUid, descriptor.alias)
 
             if (code == DELETE_KEY_TRANSACTION) {
-                if (KeyMintSecurityLevelInterceptor.getGeneratedKeyResponse(keyId) != null) {
-                    KeyMintSecurityLevelInterceptor.cleanupKeyData(keyId)
+                val wasSoftwareKey = KeyMintSecurityLevelInterceptor.getGeneratedKeyResponse(keyId) != null
+                KeyMintSecurityLevelInterceptor.cleanupKeyData(keyId)
+                if (wasSoftwareKey) {
+                    deletedSoftwareKeys.add(keyId)
                     SystemLogger.info(
                         "[TX_ID: $txId] Deleted cached keypair ${descriptor.alias}, replying with empty response."
                     )
@@ -166,6 +172,11 @@ object Keystore2Interceptor : AbstractKeystoreInterceptor() {
                 return TransactionResult.ContinueAndSkipPost
             }
 
+            if (keyId in deletedSoftwareKeys) {
+                SystemLogger.info("[TX_ID: $txId] Returning KEY_NOT_FOUND for deleted key ${descriptor.alias}")
+                return InterceptorUtils.createErrorReply(RESPONSE_KEY_NOT_FOUND)
+            }
+
             val response =
                 KeyMintSecurityLevelInterceptor.getGeneratedKeyResponse(keyId)
                     ?: return TransactionResult.Continue