diff --git a/src/main/java/com/google/firebase/auth/hash/Bcrypt.java b/src/main/java/com/google/firebase/auth/hash/Bcrypt.java
index 2b5f89029..9c55d8d56 100644
--- a/src/main/java/com/google/firebase/auth/hash/Bcrypt.java
+++ b/src/main/java/com/google/firebase/auth/hash/Bcrypt.java
@@ -24,7 +24,7 @@
  * Represents the Bcrypt password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class Bcrypt extends UserImportHash {
+public final class Bcrypt extends UserImportHash {
 
   private Bcrypt() {
     super("BCRYPT");
diff --git a/src/main/java/com/google/firebase/auth/hash/HmacMd5.java b/src/main/java/com/google/firebase/auth/hash/HmacMd5.java
index b67574358..b2ffdb852 100644
--- a/src/main/java/com/google/firebase/auth/hash/HmacMd5.java
+++ b/src/main/java/com/google/firebase/auth/hash/HmacMd5.java
@@ -20,7 +20,7 @@
  * Represents the HMAC MD5 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class HmacMd5 extends Hmac {
+public final class HmacMd5 extends Hmac {
 
   private HmacMd5(Builder builder) {
     super("HMAC_MD5", builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/HmacSha1.java b/src/main/java/com/google/firebase/auth/hash/HmacSha1.java
index a9ecefd6f..964e5e60d 100644
--- a/src/main/java/com/google/firebase/auth/hash/HmacSha1.java
+++ b/src/main/java/com/google/firebase/auth/hash/HmacSha1.java
@@ -20,7 +20,7 @@
  * Represents the HMAC SHA1 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class HmacSha1 extends Hmac {
+public final class HmacSha1 extends Hmac {
 
   private HmacSha1(Builder builder) {
     super("HMAC_SHA1", builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/HmacSha256.java b/src/main/java/com/google/firebase/auth/hash/HmacSha256.java
index 78f131cff..92917e6f3 100644
--- a/src/main/java/com/google/firebase/auth/hash/HmacSha256.java
+++ b/src/main/java/com/google/firebase/auth/hash/HmacSha256.java
@@ -20,7 +20,7 @@
  * Represents the HMAC SHA256 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class HmacSha256 extends Hmac {
+public final class HmacSha256 extends Hmac {
 
   private HmacSha256(Builder builder) {
     super("HMAC_SHA256", builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/HmacSha512.java b/src/main/java/com/google/firebase/auth/hash/HmacSha512.java
index 21e6a2b25..b5a0e09ec 100644
--- a/src/main/java/com/google/firebase/auth/hash/HmacSha512.java
+++ b/src/main/java/com/google/firebase/auth/hash/HmacSha512.java
@@ -20,7 +20,7 @@
  * Represents the HMAC SHA512 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class HmacSha512 extends Hmac {
+public final class HmacSha512 extends Hmac {
 
   private HmacSha512(Builder builder) {
     super("HMAC_SHA512", builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/Md5.java b/src/main/java/com/google/firebase/auth/hash/Md5.java
index 2abbe55ba..353b07f01 100644
--- a/src/main/java/com/google/firebase/auth/hash/Md5.java
+++ b/src/main/java/com/google/firebase/auth/hash/Md5.java
@@ -20,7 +20,7 @@
  * Represents the MD5 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class Md5 extends RepeatableHash {
+public final class Md5 extends RepeatableHash {
 
   private Md5(Builder builder) {
     super("MD5", 0, 8192, builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/Pbkdf2Sha256.java b/src/main/java/com/google/firebase/auth/hash/Pbkdf2Sha256.java
index 4c5108e35..6c3ffeff2 100644
--- a/src/main/java/com/google/firebase/auth/hash/Pbkdf2Sha256.java
+++ b/src/main/java/com/google/firebase/auth/hash/Pbkdf2Sha256.java
@@ -20,7 +20,7 @@
  * Represents the PBKDF2 SHA256 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class Pbkdf2Sha256 extends RepeatableHash {
+public final class Pbkdf2Sha256 extends RepeatableHash {
 
   private Pbkdf2Sha256(Builder builder) {
     super("PBKDF2_SHA256", 0, 120000, builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/PbkdfSha1.java b/src/main/java/com/google/firebase/auth/hash/PbkdfSha1.java
index 8afe3f4ab..647a365b3 100644
--- a/src/main/java/com/google/firebase/auth/hash/PbkdfSha1.java
+++ b/src/main/java/com/google/firebase/auth/hash/PbkdfSha1.java
@@ -20,7 +20,7 @@
  * Represents the PBKDF SHA1 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class PbkdfSha1 extends RepeatableHash {
+public final class PbkdfSha1 extends RepeatableHash {
 
   private PbkdfSha1(Builder builder) {
     super("PBKDF_SHA1", 0, 120000, builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/Sha1.java b/src/main/java/com/google/firebase/auth/hash/Sha1.java
index 385f4310c..9de01b0b8 100644
--- a/src/main/java/com/google/firebase/auth/hash/Sha1.java
+++ b/src/main/java/com/google/firebase/auth/hash/Sha1.java
@@ -20,7 +20,7 @@
  * Represents the SHA1 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class Sha1 extends RepeatableHash {
+public final class Sha1 extends RepeatableHash {
 
   private Sha1(Builder builder) {
     super("SHA1", 1, 8192, builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/Sha256.java b/src/main/java/com/google/firebase/auth/hash/Sha256.java
index f65aee19a..d0185195e 100644
--- a/src/main/java/com/google/firebase/auth/hash/Sha256.java
+++ b/src/main/java/com/google/firebase/auth/hash/Sha256.java
@@ -20,7 +20,7 @@
  * Represents the SHA256 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class Sha256 extends RepeatableHash {
+public final class Sha256 extends RepeatableHash {
 
   private Sha256(Builder builder) {
     super("SHA256", 1, 8192, builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/Sha512.java b/src/main/java/com/google/firebase/auth/hash/Sha512.java
index e582520a9..f468abe1c 100644
--- a/src/main/java/com/google/firebase/auth/hash/Sha512.java
+++ b/src/main/java/com/google/firebase/auth/hash/Sha512.java
@@ -20,7 +20,7 @@
  * Represents the SHA512 password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class Sha512 extends RepeatableHash {
+public final class Sha512 extends RepeatableHash {
 
   private Sha512(Builder builder) {
     super("SHA512", 1, 8192, builder);
diff --git a/src/main/java/com/google/firebase/auth/hash/StandardScrypt.java b/src/main/java/com/google/firebase/auth/hash/StandardScrypt.java
index 49f7d72f5..139fd114f 100644
--- a/src/main/java/com/google/firebase/auth/hash/StandardScrypt.java
+++ b/src/main/java/com/google/firebase/auth/hash/StandardScrypt.java
@@ -24,7 +24,7 @@
  * Represents the Standard Scrypt password hashing algorithm. Can be used as an instance of
  * {@link com.google.firebase.auth.UserImportHash} when importing users.
  */
-public class StandardScrypt extends UserImportHash {
+public final class StandardScrypt extends UserImportHash {
 
   private final int derivedKeyLength;
   private final int blockSize;