diff --git a/src/main/java/com/google/crypto/tink/subtle/AesSiv.java b/src/main/java/com/google/crypto/tink/subtle/AesSiv.java
index 83f0df64..b7cb23a4 100644
--- a/src/main/java/com/google/crypto/tink/subtle/AesSiv.java
+++ b/src/main/java/com/google/crypto/tink/subtle/AesSiv.java
@@ -69,6 +69,18 @@ public static DeterministicAead create(AesSivKey key) throws GeneralSecurityExce
         key.getKeyBytes().toByteArray(InsecureSecretKeyAccess.get()), key.getOutputPrefix());
   }
 
+  private static final ThreadLocal<Cipher> localAesCtrCipher =
+      new ThreadLocal<Cipher>() {
+        @Override
+        protected Cipher initialValue() {
+          try {
+            return EngineFactory.CIPHER.getInstance("AES/CTR/NoPadding");
+          } catch (GeneralSecurityException ex) {
+            throw new IllegalStateException(ex);
+          }
+        }
+      };
+
   private AesSiv(final byte[] key, Bytes outputPrefix) throws GeneralSecurityException {
     if (!FIPS.isCompatible()) {
       throw new GeneralSecurityException(
@@ -132,7 +144,7 @@ public byte[] encryptDeterministically(final byte[] plaintext, final byte[] asso
       throw new GeneralSecurityException("plaintext too long");
     }
 
-    Cipher aesCtr = EngineFactory.CIPHER.getInstance("AES/CTR/NoPadding");
+    Cipher aesCtr = localAesCtrCipher.get();
     byte[] computedIv = s2v(associatedData, plaintext);
     byte[] ivForJavaCrypto = computedIv.clone();
     ivForJavaCrypto[8] &= (byte) 0x7F; // 63th bit from the right
@@ -158,7 +170,7 @@ public byte[] decryptDeterministically(final byte[] ciphertext, final byte[] ass
       throw new GeneralSecurityException("Decryption failed (OutputPrefix mismatch).");
     }
 
-    Cipher aesCtr = EngineFactory.CIPHER.getInstance("AES/CTR/NoPadding");
+    Cipher aesCtr = localAesCtrCipher.get();
 
     byte[] expectedIv =
         Arrays.copyOfRange(
diff --git a/src/main/java/com/google/crypto/tink/subtle/PrfAesCmac.java b/src/main/java/com/google/crypto/tink/subtle/PrfAesCmac.java
index b92541a2..6a11d677 100644
--- a/src/main/java/com/google/crypto/tink/subtle/PrfAesCmac.java
+++ b/src/main/java/com/google/crypto/tink/subtle/PrfAesCmac.java
@@ -48,11 +48,23 @@ public final class PrfAesCmac implements Prf {
   @SuppressWarnings("Immutable")
   private byte[] subKey2;
 
+  private static final ThreadLocal<Cipher> localAesCipher =
+      new ThreadLocal<Cipher>() {
+        @Override
+        protected Cipher initialValue() {
+          try {
+            return EngineFactory.CIPHER.getInstance("AES/ECB/NoPadding");
+          } catch (GeneralSecurityException ex) {
+            throw new IllegalStateException(ex);
+          }
+        }
+      };
+
   private static Cipher instance() throws GeneralSecurityException {
     if (!FIPS.isCompatible()) {
       throw new GeneralSecurityException("Can not use AES-CMAC in FIPS-mode.");
     }
-    return EngineFactory.CIPHER.getInstance("AES/ECB/NoPadding");
+    return localAesCipher.get();
   }
 
   public PrfAesCmac(final byte[] key) throws GeneralSecurityException {