diff --git a/ext/awscrt.c b/ext/awscrt.c
index c72b758..ef976bc 100644
--- a/ext/awscrt.c
+++ b/ext/awscrt.c
@@ -11,5 +11,5 @@
 #include "http.c"
 #include "signing.c"
 #include "stream.c"
-// #include "hash.c"
+#include "hash.c"
 #include "crc.c"
diff --git a/ext/awscrt.stub.php b/ext/awscrt.stub.php
index b7f7a10..2cdee08 100644
--- a/ext/awscrt.stub.php
+++ b/ext/awscrt.stub.php
@@ -121,4 +121,16 @@ function aws_crt_sign_request_aws(int $signable, int $signing_config, object $on
 
 function aws_crt_crc32(string $input, int $prev): int {}
 
-function aws_crt_crc32c(string $input, int $prev): int {}
\ No newline at end of file
+function aws_crt_crc32c(string $input, int $prev): int {}
+
+function aws_crt_sha1_new(): int {}
+
+function aws_crt_sha256_new(): int {}
+
+function aws_crt_md5_new(): int {}
+
+function aws_crt_hash_update(int $hash, string $buffer): int{}
+
+function aws_crt_hash_digest(int $hash, int $truncate_to, int $length): string {}
+
+function aws_crt_hash_destroy(int $hash): void {}
\ No newline at end of file
diff --git a/ext/awscrt_arginfo.h b/ext/awscrt_arginfo.h
index 7923b3d..b59084e 100644
--- a/ext/awscrt_arginfo.h
+++ b/ext/awscrt_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit the .stub.php file instead.
- * Stub hash: 36d4e512f02a12c10689eb9b0941bcd7837fbf1d */
+ * Stub hash: 271adcfe560a474d149e60d7951a45a93a9259d3 */
 
 ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_aws_crt_last_error, 0, 0, IS_LONG, 0)
 ZEND_END_ARG_INFO()
@@ -235,6 +235,28 @@ ZEND_END_ARG_INFO()
 
 #define arginfo_aws_crt_crc32c arginfo_aws_crt_crc32
 
+#define arginfo_aws_crt_sha1_new arginfo_aws_crt_last_error
+
+#define arginfo_aws_crt_sha256_new arginfo_aws_crt_last_error
+
+#define arginfo_aws_crt_md5_new arginfo_aws_crt_last_error
+
+ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_aws_crt_hash_update, 0, 2, IS_LONG, 0)
+	ZEND_ARG_TYPE_INFO(0, hash, IS_LONG, 0)
+	ZEND_ARG_TYPE_INFO(0, buffer, IS_STRING, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_aws_crt_hash_digest, 0, 3, IS_STRING, 0)
+	ZEND_ARG_TYPE_INFO(0, hash, IS_LONG, 0)
+	ZEND_ARG_TYPE_INFO(0, truncate_to, IS_LONG, 0)
+	ZEND_ARG_TYPE_INFO(0, length, IS_LONG, 0)
+ZEND_END_ARG_INFO()
+
+ZEND_BEGIN_ARG_WITH_RETURN_TYPE_INFO_EX(arginfo_aws_crt_hash_destroy, 0, 1, IS_VOID, 0)
+	ZEND_ARG_TYPE_INFO(0, hash, IS_LONG, 0)
+ZEND_END_ARG_INFO()
+
+
 ZEND_FUNCTION(aws_crt_last_error);
 ZEND_FUNCTION(aws_crt_error_name);
 ZEND_FUNCTION(aws_crt_error_str);
@@ -294,6 +316,12 @@ ZEND_FUNCTION(aws_crt_signing_result_apply_to_http_request);
 ZEND_FUNCTION(aws_crt_sign_request_aws);
 ZEND_FUNCTION(aws_crt_crc32);
 ZEND_FUNCTION(aws_crt_crc32c);
+ZEND_FUNCTION(aws_crt_sha1_new);
+ZEND_FUNCTION(aws_crt_sha256_new);
+ZEND_FUNCTION(aws_crt_md5_new);
+ZEND_FUNCTION(aws_crt_hash_update);
+ZEND_FUNCTION(aws_crt_hash_digest);
+ZEND_FUNCTION(aws_crt_hash_destroy);
 
 
 static const zend_function_entry ext_functions[] = {
@@ -356,5 +384,11 @@ static const zend_function_entry ext_functions[] = {
 	ZEND_FE(aws_crt_sign_request_aws, arginfo_aws_crt_sign_request_aws)
 	ZEND_FE(aws_crt_crc32, arginfo_aws_crt_crc32)
 	ZEND_FE(aws_crt_crc32c, arginfo_aws_crt_crc32c)
+	ZEND_FE(aws_crt_sha1_new, arginfo_aws_crt_sha1_new)
+	ZEND_FE(aws_crt_sha256_new, arginfo_aws_crt_sha256_new)
+	ZEND_FE(aws_crt_md5_new, arginfo_aws_crt_md5_new)
+	ZEND_FE(aws_crt_hash_update, arginfo_aws_crt_hash_update)
+	ZEND_FE(aws_crt_hash_digest, arginfo_aws_crt_hash_digest)
+	ZEND_FE(aws_crt_hash_destroy, arginfo_aws_crt_hash_destroy)
 	ZEND_FE_END
 };
diff --git a/ext/hash.c b/ext/hash.c
new file mode 100644
index 0000000..acff398
--- /dev/null
+++ b/ext/hash.c
@@ -0,0 +1,58 @@
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+#include "php_aws_crt.h"
+
+PHP_FUNCTION(aws_crt_sha1_new) {
+    aws_crt_hash *hash = aws_crt_sha1_new();
+    RETURN_LONG((zend_ulong)hash);
+}
+
+PHP_FUNCTION(aws_crt_sha256_new) {
+    aws_crt_hash *hash = aws_crt_sha256_new();
+    RETURN_LONG((zend_ulong)hash);
+}
+
+PHP_FUNCTION(aws_crt_md5_new) {
+    aws_crt_hash *hash = aws_crt_md5_new();
+    RETURN_LONG((zend_ulong)hash);
+}
+
+PHP_FUNCTION(aws_crt_hash_update) {
+    zend_ulong php_hash = 0;
+    const char * buffer = NULL;
+    size_t len = 0;
+    aws_php_parse_parameters("ls", &php_hash, &buffer, &len);
+    aws_crt_hash *hash = (void *) php_hash;
+    RETURN_LONG((zend_ulong) aws_crt_hash_update(hash, (uint8_t *)buffer, (uint32_t) len));
+}
+
+PHP_FUNCTION(aws_crt_hash_digest) {
+    zend_ulong php_hash = 0;
+    size_t truncate_to = 0;
+    size_t length = 0;
+    aws_php_parse_parameters("lll", &php_hash, &truncate_to, &length);
+    aws_crt_hash *hash = (void *) php_hash;
+    if (truncate_to != 0 && length > truncate_to) {
+        length = truncate_to;
+    }
+    uint8_t *output = aws_crt_hash_digest(hash, truncate_to);
+    size_t len = strlen((const char *)output) + 1;
+    char arr[len];  // Make sure there's enough space
+    strcpy(arr, (char *) output);
+    printf(arr);
+    zval *php_output = NULL;
+    ZVAL_STRINGL(php_output, (const char *)output, length);
+    aws_mem_release(aws_crt_default_allocator(), output);
+    // copy false, destroy false?
+    RETURN_ZVAL(php_output, false, false);
+}
+
+PHP_FUNCTION(aws_crt_hash_destroy) {
+    zend_ulong php_hash = 0;
+    aws_php_parse_parameters("l", &php_hash);
+    aws_crt_hash *hash = (void *) php_hash;
+    aws_crt_hash_destroy(hash);
+}
\ No newline at end of file
diff --git a/src/AWS/CRT/CRT.php b/src/AWS/CRT/CRT.php
index 5410496..74b9cc8 100644
--- a/src/AWS/CRT/CRT.php
+++ b/src/AWS/CRT/CRT.php
@@ -346,11 +346,35 @@ final class CRT {
         return self::$impl->aws_crt_sign_request_aws($signable, $signing_config, $on_complete, $user_data);
     }
 
-    public static function crc32($input, $previous = 0) {
+    function sha1_new() {
+        return self::$impl->aws_crt_sha1_new();
+    }
+
+    function sha256_new() {
+        return self::$impl->aws_crt_sha256_new();
+    }
+
+    function md5_new() {
+        return self::$impl->aws_crt_md5_new();
+    }
+
+    function hash_update($hash, $buffer) {
+        return self::$impl->aws_crt_hash_update($hash, $buffer);
+    }
+
+    function hash_digest($hash, $truncate_to, $length) {
+        return self::$impl->aws_crt_hash_digest($hash, $truncate_to, $length);
+    }
+
+    function hash_destroy($hash) {
+        return self::$impl->aws_crt_hash_destroy($hash);
+    }
+
+    public static function crc32($input, $previous) {
         return self::$impl->aws_crt_crc32($input, $previous);
     }
 
-    public static function crc32c($input, $previous = 0) {
+    public static function crc32c($input, $previous) {
         return self::$impl->aws_crt_crc32c($input, $previous);
     }
 }
diff --git a/src/AWS/CRT/Cal/Hash.php b/src/AWS/CRT/Cal/Hash.php
new file mode 100644
index 0000000..1fd4dd8
--- /dev/null
+++ b/src/AWS/CRT/Cal/Hash.php
@@ -0,0 +1,41 @@
+<?php
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+namespace AWS\CRT\Cal;
+
+use AWS\CRT\NativeResource;
+
+class Hash extends NativeResource {
+    private function __construct($hash, $len) {
+        parent::__construct();
+        $this->hash = $hash;
+        $this->len = $len;
+    }
+
+    public static function sha1_new() {
+        return new Hash(self::$crt->sha1_new(), 20);
+    }
+
+    public static function sha256_new() {
+        return new Hash(self::$crt->sha256_new(), 32);
+    }
+
+    public static function md5_new() {
+        return new Hash(self::$crt->md5_new(), 16);
+    }
+
+    public function update($buffer) {
+        self::$crt->hash_update($this->hash, $buffer);
+    }
+
+    public function digest($truncate_to) {
+        return self::$crt->hash_digest($this->hash, $truncate_to, $this->len);
+    }
+
+    function __destruct() {
+        self::$crt->hash_destroy($this->hash);
+        parent::__destruct();
+    }
+}
\ No newline at end of file
diff --git a/tests/CrcTest.php b/tests/CrcTest.php
index 5c4b5af..72717a4 100644
--- a/tests/CrcTest.php
+++ b/tests/CrcTest.php
@@ -11,7 +11,7 @@ final class CrcTest extends CrtTestCase {
 
     public function testCrc32ZeroesOneShot() {
         $input = implode(array_map("chr", array_fill(0, 32, 0)));
-        $output = CRT::crc32($input);
+        $output = CRT::crc32($input, 0);
         $expected = 0x190A55AD;
         $this->assertEquals($output, $expected);
     }
@@ -25,6 +25,54 @@ final class CrcTest extends CrtTestCase {
         $this->assertEquals($output, $expected);
     }
 
+    public function testCrc32ValuesOneShot() {
+        $input = implode(array_map("chr", range(0, 31)));
+        $output = CRT::crc32($input, 0);
+        $expected = 0x91267E8A;
+        $this->assertEquals($output, $expected);
+    }
+
+    public function testCrc32ValuesIterated() {
+        $output = 0;
+        foreach (range(0, 31) as $n) {
+            $output = CRT::crc32(chr($n), $output);
+        }
+        $expected = 0x91267E8A;
+        $this->assertEquals($output, $expected);
+    }
+
+    public function testCrc32cZeroesOneShot() {
+        $input = implode(array_map("chr", array_fill(0, 32, 0)));
+        $output = CRT::crc32c($input, 0);
+        $expected = 0x8A9136AA;
+        $this->assertEquals($output, $expected);
+    }
+
+    public function testCrc32cZeroesIterated() {
+        $output = 0;
+        for ($i = 0; $i < 32; $i++) {
+            $output = CRT::crc32c("\x00", $output);
+        }
+        $expected = 0x8A9136AA;
+        $this->assertEquals($output, $expected);
+    }
+
+    public function testCrc32cValuesOneShot() {
+        $input = implode(array_map("chr", range(0, 31)));
+        $output = CRT::crc32c($input, 0);
+        $expected = 0x46DD794E;
+        $this->assertEquals($output, $expected);
+    }
+
+    public function testCrc32ZeroesIterated() {
+        $output = 0;
+        for ($i = 0; $i < 32; $i++) {
+            $output = CRT::crc32("\x00", $output);
+        }
+        $expected = 0x190A55AD;
+        $this->assertEquals($output, $expected);
+    }
+
     public function testCrc32ValuesOneShot() {
         $input = implode(array_map("chr", range(0, 31)));
         $output = CRT::crc32($input);
diff --git a/tests/HashTest.php b/tests/HashTest.php
new file mode 100644
index 0000000..be237ba
--- /dev/null
+++ b/tests/HashTest.php
@@ -0,0 +1,20 @@
+<?php
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+use AWS\CRT\CRT;
+use AWS\CRT\Cal\Hash;
+
+require_once('common.inc');
+
+final class HashTest extends CrtTestCase {
+
+    public function testSha256Empty() {
+        $h = Hash::sha256_new();
+        $digest = $h->digest(0);
+        $expected = '\xe3\xb0\xc4\x42\x98\xfc\x1c\x14\x9a\xfb\xf4\xc8\x99\x6f\xb9\x24\x27\xae\x41\xe4\x64\x9b\x93\x4c\xa4\x95\x99\x1b\x78\x52\xb8\x55';
+        // $expected = 'test2';
+        $this->assertEquals($expected, $digest);
+    }
+}
\ No newline at end of file