diff --git a/service/pom.xml b/service/pom.xml
index 41d7f497f..57eb6c922 100644
--- a/service/pom.xml
+++ b/service/pom.xml
@@ -53,9 +53,9 @@
       <version>${project.version}</version>
     </dependency>
     <dependency>
-      <groupId>org.whispersystems</groupId>
-      <artifactId>signal-client-java</artifactId>
-      <version>0.10.0</version>
+      <groupId>org.signal</groupId>
+      <artifactId>zkgroup-java</artifactId>
+      <version>0.8.2</version>
     </dependency>
     <dependency>
       <groupId>org.whispersystems</groupId>
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/controllers/SubscriptionController.java b/service/src/main/java/org/whispersystems/textsecuregcm/controllers/SubscriptionController.java
index 8c402a309..3b9c50eda 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/controllers/SubscriptionController.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/controllers/SubscriptionController.java
@@ -703,7 +703,7 @@ public class SubscriptionController {
       this.receiptCredentialRequest = receiptCredentialRequest;
     }
 
-    @NotEmpty
+    @ExactlySize(ReceiptCredentialRequest.SIZE)
     public byte[] getReceiptCredentialRequest() {
       return receiptCredentialRequest;
     }
@@ -719,7 +719,7 @@ public class SubscriptionController {
       this.receiptCredentialResponse = receiptCredentialResponse;
     }
 
-    @NotEmpty
+    @ExactlySize(ReceiptCredentialResponse.SIZE)
     public byte[] getReceiptCredentialResponse() {
       return receiptCredentialResponse;
     }
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/entities/RedeemReceiptRequest.java b/service/src/main/java/org/whispersystems/textsecuregcm/entities/RedeemReceiptRequest.java
index f01ae859d..ab72a31ab 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/entities/RedeemReceiptRequest.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/entities/RedeemReceiptRequest.java
@@ -28,6 +28,7 @@ public class RedeemReceiptRequest {
   }
 
   @NotEmpty
+  @ExactlySize({ReceiptCredentialPresentation.SIZE})
   public byte[] getReceiptCredentialPresentation() {
     return receiptCredentialPresentation;
   }
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/storage/IssuedReceiptsManagerTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/storage/IssuedReceiptsManagerTest.java
index 486c85172..2092516dd 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/storage/IssuedReceiptsManagerTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/storage/IssuedReceiptsManagerTest.java
@@ -56,7 +56,7 @@ class IssuedReceiptsManagerTest {
   @Test
   void testRecordIssuance() {
     Instant now = Instant.ofEpochSecond(NOW_EPOCH_SECONDS);
-    byte[] request1 = new byte[20];
+    byte[] request1 = new byte[ReceiptCredentialRequest.SIZE];
     SECURE_RANDOM.nextBytes(request1);
     when(receiptCredentialRequest.serialize()).thenReturn(request1);
     CompletableFuture<Void> future = issuedReceiptsManager.recordIssuance("item-1", receiptCredentialRequest, now);
@@ -67,7 +67,7 @@ class IssuedReceiptsManagerTest {
     assertThat(future).succeedsWithin(Duration.ofSeconds(3));
 
     // same item with new request should fail
-    byte[] request2 = new byte[20];
+    byte[] request2 = new byte[ReceiptCredentialRequest.SIZE];
     SECURE_RANDOM.nextBytes(request2);
     when(receiptCredentialRequest.serialize()).thenReturn(request2);
     future = issuedReceiptsManager.recordIssuance("item-1", receiptCredentialRequest, now);
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/tests/controllers/DonationControllerTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/tests/controllers/DonationControllerTest.java
index 99bbbfbbc..baed628cf 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/tests/controllers/DonationControllerTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/tests/controllers/DonationControllerTest.java
@@ -120,7 +120,7 @@ class DonationControllerTest {
     receiptSerialBytes = new byte[ReceiptSerial.SIZE];
     SECURE_RANDOM.nextBytes(receiptSerialBytes);
     receiptSerial = new ReceiptSerial(receiptSerialBytes);
-    presentation = new byte[25];
+    presentation = new byte[ReceiptCredentialPresentation.SIZE];
     SECURE_RANDOM.nextBytes(presentation);
     receiptCredentialPresentationFactory = mock(DonationController.ReceiptCredentialPresentationFactory.class);
     receiptCredentialPresentation = mock(ReceiptCredentialPresentation.class);