diff --git a/_inc/lib/debugger/class-jetpack-cxn-tests.php b/_inc/lib/debugger/class-jetpack-cxn-tests.php
index e6854370007e..b8dc0949a219 100644
--- a/_inc/lib/debugger/class-jetpack-cxn-tests.php
+++ b/_inc/lib/debugger/class-jetpack-cxn-tests.php
@@ -5,6 +5,7 @@
  * @package Jetpack
  */
 
+
 /**
  * Class Jetpack_Cxn_Tests contains all of the actual tests.
  */
diff --git a/class.jetpack-client.php b/class.jetpack-client.php
index cabb2e0374e8..14858652284f 100644
--- a/class.jetpack-client.php
+++ b/class.jetpack-client.php
@@ -54,8 +54,6 @@ public static function remote_request( $args, $body = null ) {
 
 		$token_key = sprintf( '%s:%d:%d', $token_key, JETPACK__API_VERSION, $token->external_user_id );
 
-		require_once JETPACK__PLUGIN_DIR . 'class.jetpack-signature.php';
-
 		$time_diff = (int) Jetpack_Options::get_option( 'time_diff' );
 		$jetpack_signature = new Jetpack_Signature( $token->secret, $time_diff );
 
@@ -89,7 +87,7 @@ public static function remote_request( $args, $body = null ) {
 				return new Jetpack_Error( 'invalid_body', 'Body is malformed.' );
 			}
 
-			$body_hash = jetpack_sha1_base64( $body_to_hash );
+			$body_hash = Jetpack::connection()->sha1_base64( $body_to_hash );
 		}
 
 		$auth = array(
diff --git a/class.jetpack.php b/class.jetpack.php
index 560dbd468d5b..4930c3b67dc2 100644
--- a/class.jetpack.php
+++ b/class.jetpack.php
@@ -5203,8 +5203,6 @@ function verify_xml_rpc_signature() {
 			return false;
 		}
 
-		require_once JETPACK__PLUGIN_DIR . 'class.jetpack-signature.php';
-
 		$jetpack_signature = new Jetpack_Signature( $token->secret, (int) Jetpack_Options::get_option( 'time_diff' ) );
 		if ( isset( $_POST['_jetpack_is_multipart'] ) ) {
 			$post_data   = $_POST;
@@ -5814,8 +5812,6 @@ function add_token_to_login_redirect_json_api_authorization( $redirect_to, $orig
 	 * @param null|array $environment
 	 */
 	function verify_json_api_authorization_request( $environment = null ) {
-		require_once JETPACK__PLUGIN_DIR . 'class.jetpack-signature.php';
-
 		$environment = is_null( $environment )
 			? $_REQUEST
 			: $environment;
diff --git a/composer.lock b/composer.lock
index cb686138e673..5ed8edf71db6 100644
--- a/composer.lock
+++ b/composer.lock
@@ -8,12 +8,11 @@
     "packages": [
         {
             "name": "automattic/jetpack-asset-tools",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/asset-tools",
-                "reference": "d425ff2ef48f7e4c323507ca583e4065f7f107a6",
-                "shasum": null
+                "reference": "d425ff2ef48f7e4c323507ca583e4065f7f107a6"
             },
             "require": {
                 "automattic/jetpack-constants": "@dev"
@@ -31,12 +30,11 @@
         },
         {
             "name": "automattic/jetpack-connection",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/connection",
-                "reference": "eb2ab1a317d710fbe651a20fa580d523e303d848",
-                "shasum": null
+                "reference": "0a0e293d73c17d59376590d56e5667b169d26877"
             },
             "require": {
                 "automattic/jetpack-constants": "@dev",
@@ -50,7 +48,10 @@
             "autoload": {
                 "psr-4": {
                     "Automattic\\Jetpack\\Connection\\": "src"
-                }
+                },
+                "classmap": [
+                    "legacy"
+                ]
             },
             "scripts": {
                 "phpunit": [
@@ -65,12 +66,11 @@
         },
         {
             "name": "automattic/jetpack-constants",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/constants",
-                "reference": "a6ab6360f4b48962ec7d62b06b39d1470b1dbe95",
-                "shasum": null
+                "reference": "a6ab6360f4b48962ec7d62b06b39d1470b1dbe95"
             },
             "require-dev": {
                 "phpunit/phpunit": "^5.7 || ^6.5 || ^7.5"
@@ -94,12 +94,11 @@
         },
         {
             "name": "automattic/jetpack-jitm",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/jitm",
-                "reference": "38af4dd23b02753405d0f718f87df55259979591",
-                "shasum": null
+                "reference": "38af4dd23b02753405d0f718f87df55259979591"
             },
             "require": {
                 "automattic/jetpack-asset-tools": "@dev",
@@ -132,12 +131,11 @@
         },
         {
             "name": "automattic/jetpack-logo",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/logo",
-                "reference": "d8a31dfd40166c4867fa2c526a03d9df481d5610",
-                "shasum": null
+                "reference": "d8a31dfd40166c4867fa2c526a03d9df481d5610"
             },
             "require-dev": {
                 "php-mock/php-mock": "^2.1",
@@ -162,12 +160,11 @@
         },
         {
             "name": "automattic/jetpack-options",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/options",
-                "reference": "78220bf7d3c1a3a5ed4edb77462e84982b3c408f",
-                "shasum": null
+                "reference": "78220bf7d3c1a3a5ed4edb77462e84982b3c408f"
             },
             "require": {
                 "automattic/jetpack-constants": "@dev"
@@ -189,12 +186,11 @@
         },
         {
             "name": "automattic/jetpack-sync",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/sync",
-                "reference": "b6c34729a2a37b5a485add5d357ff018654e3e35",
-                "shasum": null
+                "reference": "b6c34729a2a37b5a485add5d357ff018654e3e35"
             },
             "require": {
                 "automattic/jetpack-constants": "@dev",
@@ -213,12 +209,11 @@
         },
         {
             "name": "automattic/jetpack-tracking",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/tracking",
-                "reference": "bf2c5cf51eec2e1ad21955c05c692ef2815875b9",
-                "shasum": null
+                "reference": "bf2c5cf51eec2e1ad21955c05c692ef2815875b9"
             },
             "require": {
                 "automattic/jetpack-options": "@dev"
@@ -368,12 +363,11 @@
     "packages-dev": [
         {
             "name": "automattic/jetpack-autoloader",
-            "version": "dev-update/bye-constants-manager",
+            "version": "dev-add/jetpack-signature-to-connection",
             "dist": {
                 "type": "path",
                 "url": "./packages/autoloader",
-                "reference": "8c7dc6036bf6125c31a574c14c6b0521247410ed",
-                "shasum": null
+                "reference": "8c7dc6036bf6125c31a574c14c6b0521247410ed"
             },
             "require": {
                 "composer-plugin-api": "^1.1"
diff --git a/functions.compat.php b/functions.compat.php
index bc7e6fbd822e..4e1f47af4a14 100644
--- a/functions.compat.php
+++ b/functions.compat.php
@@ -1,5 +1,7 @@
 <?php
 
+use \Automattic\Jetpack\Connection\Manager as Connection_Manager;
+
 /**
 * Required for class.media-extractor.php to match expected function naming convention.
 *
@@ -88,3 +90,11 @@ function wp_in( $needle, $haystack ) {
 		return false !== strpos( $haystack, $needle );
 	}
 endif;
+
+/**
+ * @deprecated 7.5 Use Connection_Manager instead.
+ */
+function jetpack_sha1_base64( $text ) {
+	$connection = new Connection_Manager();
+	return $connection->sha1_base64( $text );
+}
diff --git a/jetpack.php b/jetpack.php
index f69b9a00f1c0..f882f9d7a7da 100644
--- a/jetpack.php
+++ b/jetpack.php
@@ -47,6 +47,12 @@
 	. '-----END PUBLIC KEY-----' . "\r\n"
 );
 
+// These constants can be set in wp-config.php to ensure sites behind proxies will still work.
+// Setting these constants, though, is *not* the preferred method. It's better to configure
+// the proxy to send the X-Forwarded-Port header.
+defined( 'JETPACK_SIGNATURE__HTTP_PORT'  ) or define( 'JETPACK_SIGNATURE__HTTP_PORT' , 80  );
+defined( 'JETPACK_SIGNATURE__HTTPS_PORT' ) or define( 'JETPACK_SIGNATURE__HTTPS_PORT', 443 );
+
 /**
  * Returns the location of Jetpack's lib directory. This filter is applied
  * in require_lib().
diff --git a/packages/connection/composer.json b/packages/connection/composer.json
index 1f75092bf68a..d2c1658f5b06 100644
--- a/packages/connection/composer.json
+++ b/packages/connection/composer.json
@@ -14,7 +14,10 @@
 	"autoload": {
 		"psr-4": {
 			"Automattic\\Jetpack\\Connection\\": "src"
-		}
+		},
+		"classmap": [
+			"legacy"
+		]
 	},
 	"scripts": {
 		"phpunit": [
diff --git a/class.jetpack-signature.php b/packages/connection/legacy/class.jetpack-signature.php
similarity index 56%
rename from class.jetpack-signature.php
rename to packages/connection/legacy/class.jetpack-signature.php
index 8d925d7d074d..3a7e6fc39098 100644
--- a/class.jetpack-signature.php
+++ b/packages/connection/legacy/class.jetpack-signature.php
@@ -1,10 +1,6 @@
 <?php
 
-// These constants can be set in wp-config.php to ensure sites behind proxies will still work.
-// Setting these constants, though, is *not* the preferred method. It's better to configure
-// the proxy to send the X-Forwarded-Port header.
-defined( 'JETPACK_SIGNATURE__HTTP_PORT'  ) or define( 'JETPACK_SIGNATURE__HTTP_PORT' , 80  );
-defined( 'JETPACK_SIGNATURE__HTTPS_PORT' ) or define( 'JETPACK_SIGNATURE__HTTPS_PORT', 443 );
+use \Automattic\Jetpack\Connection\Manager as Connection_Manager;
 
 class Jetpack_Signature {
 	public $token;
@@ -12,19 +8,20 @@ class Jetpack_Signature {
 
 	function __construct( $access_token, $time_diff = 0 ) {
 		$secret = explode( '.', $access_token );
-		if ( 2 != count( $secret ) )
+		if ( 2 != count( $secret ) ) {
 			return;
+		}
 
-		$this->token  = $secret[0];
-		$this->secret = $secret[1];
+		$this->token     = $secret[0];
+		$this->secret    = $secret[1];
 		$this->time_diff = $time_diff;
 	}
 
 	function sign_current_request( $override = array() ) {
 		if ( isset( $override['scheme'] ) ) {
 			$scheme = $override['scheme'];
-			if ( !in_array( $scheme, array( 'http', 'https' ) ) ) {
-				return new Jetpack_Error( 'invalid_scheme', 'Invalid URL scheme' );
+			if ( ! in_array( $scheme, array( 'http', 'https' ) ) ) {
+				return new WP_Error( 'invalid_scheme', 'Invalid URL scheme' );
 			}
 		} else {
 			if ( is_ssl() ) {
@@ -36,6 +33,7 @@ function sign_current_request( $override = array() ) {
 
 		$host_port = isset( $_SERVER['HTTP_X_FORWARDED_PORT'] ) ? $_SERVER['HTTP_X_FORWARDED_PORT'] : $_SERVER['SERVER_PORT'];
 
+		$connection = new Connection_Manager();
 		/**
 		 * Note: This port logic is tested in the Jetpack_Cxn_Tests->test__server_port_value() test.
 		 * Please update the test if any changes are made in this logic.
@@ -43,28 +41,30 @@ function sign_current_request( $override = array() ) {
 		if ( is_ssl() ) {
 			// 443: Standard Port
 			// 80: Assume we're behind a proxy without X-Forwarded-Port. Hardcoding "80" here means most sites
-			//     with SSL termination proxies (self-served, Cloudflare, etc.) don't need to fiddle with
-			//     the JETPACK_SIGNATURE__HTTPS_PORT constant. The code also implies we can't talk to a
-			//     site at https://example.com:80/ (which would be a strange configuration).
+			// with SSL termination proxies (self-served, Cloudflare, etc.) don't need to fiddle with
+			// the JETPACK_SIGNATURE__HTTPS_PORT constant. The code also implies we can't talk to a
+			// site at https://example.com:80/ (which would be a strange configuration).
 			// JETPACK_SIGNATURE__HTTPS_PORT: Set this constant in wp-config.php to the back end webserver's port
-			//                                if the site is behind a proxy running on port 443 without
-			//                                X-Forwarded-Port and the back end's port is *not* 80. It's better,
-			//                                though, to configure the proxy to send X-Forwarded-Port.
-			$port = in_array( $host_port, array( 443, 80, JETPACK_SIGNATURE__HTTPS_PORT ) ) ? '' : $host_port;
+			// if the site is behind a proxy running on port 443 without
+			// X-Forwarded-Port and the back end's port is *not* 80. It's better,
+			// though, to configure the proxy to send X-Forwarded-Port.
+			$https_port = defined( 'JETPACK_SIGNATURE__HTTPS_PORT' ) ? JETPACK_SIGNATURE__HTTPS_PORT : 443;
+			$port       = in_array( $host_port, array( 443, 80, $https_port ) ) ? '' : $host_port;
 		} else {
 			// 80: Standard Port
 			// JETPACK_SIGNATURE__HTTPS_PORT: Set this constant in wp-config.php to the back end webserver's port
-			//                                if the site is behind a proxy running on port 80 without
-			//                                X-Forwarded-Port. It's better, though, to configure the proxy to
-			//                                send X-Forwarded-Port.
-			$port = in_array( $host_port, array( 80, JETPACK_SIGNATURE__HTTP_PORT ) ) ? '' : $host_port;
+			// if the site is behind a proxy running on port 80 without
+			// X-Forwarded-Port. It's better, though, to configure the proxy to
+			// send X-Forwarded-Port.
+			$http_port = defined( 'JETPACK_SIGNATURE__HTTP_PORT' ) ? JETPACK_SIGNATURE__HTTP_PORT : 80;
+			$port      = in_array( $host_port, array( 80, $http_port ) ) ? '' : $host_port;
 		}
 
 		$url = "{$scheme}://{$_SERVER['HTTP_HOST']}:{$port}" . stripslashes( $_SERVER['REQUEST_URI'] );
 
 		if ( array_key_exists( 'body', $override ) && ! empty( $override['body'] ) ) {
 			$body = $override['body'];
-		} else if ( 'POST' == strtoupper( $_SERVER['REQUEST_METHOD'] ) ) {
+		} elseif ( 'POST' == strtoupper( $_SERVER['REQUEST_METHOD'] ) ) {
 			$body = isset( $GLOBALS['HTTP_RAW_POST_DATA'] ) ? $GLOBALS['HTTP_RAW_POST_DATA'] : null;
 
 			// Convert the $_POST to the body, if the body was empty. This is how arrays are hashed
@@ -74,7 +74,7 @@ function sign_current_request( $override = array() ) {
 					$body = $_POST;
 				}
 			}
-		} else if ( 'PUT' == strtoupper( $_SERVER['REQUEST_METHOD'] ) ) {
+		} elseif ( 'PUT' == strtoupper( $_SERVER['REQUEST_METHOD'] ) ) {
 			// This is a little strange-looking, but there doesn't seem to be another way to get the PUT body
 			$raw_put_data = file_get_contents( 'php://input' );
 			parse_str( $raw_put_data, $body );
@@ -95,10 +95,10 @@ function sign_current_request( $override = array() ) {
 
 		$a = array();
 		foreach ( array( 'token', 'timestamp', 'nonce', 'body-hash' ) as $parameter ) {
-			if ( isset( $override[$parameter] ) ) {
-				$a[$parameter] = $override[$parameter];
+			if ( isset( $override[ $parameter ] ) ) {
+				$a[ $parameter ] = $override[ $parameter ];
 			} else {
-				$a[$parameter] = isset( $_GET[$parameter] ) ? stripslashes( $_GET[$parameter] ) : '';
+				$a[ $parameter ] = isset( $_GET[ $parameter ] ) ? stripslashes( $_GET[ $parameter ] ) : '';
 			}
 		}
 
@@ -108,18 +108,18 @@ function sign_current_request( $override = array() ) {
 
 	// body_hash v. body-hash is annoying.  Refactor to accept an array?
 	function sign_request( $token = '', $timestamp = 0, $nonce = '', $body_hash = '', $method = '', $url = '', $body = null, $verify_body_hash = true ) {
-		if ( !$this->secret ) {
-			return new Jetpack_Error( 'invalid_secret', 'Invalid secret' );
+		if ( ! $this->secret ) {
+			return new WP_Error( 'invalid_secret', 'Invalid secret' );
 		}
 
-		if ( !$this->token ) {
-			return new Jetpack_Error( 'invalid_token', 'Invalid token' );
+		if ( ! $this->token ) {
+			return new WP_Error( 'invalid_token', 'Invalid token' );
 		}
 
 		list( $token ) = explode( '.', $token );
 
 		if ( 0 !== strpos( $token, "$this->token:" ) ) {
-			return new Jetpack_Error( 'token_mismatch', 'Incorrect token' );
+			return new WP_Error( 'token_mismatch', 'Incorrect token' );
 		}
 
 		// If we got an array at this point, let's encode it, so we can see what it looks like as a string.
@@ -133,61 +133,62 @@ function sign_request( $token = '', $timestamp = 0, $nonce = '', $body_hash = ''
 		}
 
 		$required_parameters = array( 'token', 'timestamp', 'nonce', 'method', 'url' );
-		if ( !is_null( $body ) ) {
+		if ( ! is_null( $body ) ) {
 			$required_parameters[] = 'body_hash';
-			if ( !is_string( $body ) ) {
-				return new Jetpack_Error( 'invalid_body', 'Body is malformed.' );
+			if ( ! is_string( $body ) ) {
+				return new WP_Error( 'invalid_body', 'Body is malformed.' );
 			}
 		}
 
 		foreach ( $required_parameters as $required ) {
-			if ( !is_scalar( $$required ) ) {
-				return new Jetpack_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is malformed.', str_replace( '_', '-', $required ) ) );
+			if ( ! is_scalar( $$required ) ) {
+				return new WP_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is malformed.', str_replace( '_', '-', $required ) ) );
 			}
 
-			if ( !strlen( $$required ) ) {
-				return new Jetpack_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is missing.', str_replace( '_', '-', $required ) ) );
+			if ( ! strlen( $$required ) ) {
+				return new WP_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is missing.', str_replace( '_', '-', $required ) ) );
 			}
 		}
 
 		if ( empty( $body ) ) {
 			if ( $body_hash ) {
-				return new Jetpack_Error( 'invalid_body_hash', 'The body hash does not match.' );
+				return new WP_Error( 'invalid_body_hash', 'The body hash does not match.' );
 			}
 		} else {
-			if ( $verify_body_hash && jetpack_sha1_base64( $body ) !== $body_hash ) {
-				return new Jetpack_Error( 'invalid_body_hash', 'The body hash does not match.' );
+			$connection = new Connection_Manager();
+			if ( $verify_body_hash && $connection->sha1_base64( $body ) !== $body_hash ) {
+				return new WP_Error( 'invalid_body_hash', 'The body hash does not match.' );
 			}
 		}
 
 		$parsed = parse_url( $url );
-		if ( !isset( $parsed['host'] ) ) {
-			return new Jetpack_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is malformed.', 'url' ) );
+		if ( ! isset( $parsed['host'] ) ) {
+			return new WP_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is malformed.', 'url' ) );
 		}
 
-		if ( !empty( $parsed['port'] ) ) {
+		if ( ! empty( $parsed['port'] ) ) {
 			$port = $parsed['port'];
 		} else {
 			if ( 'http' == $parsed['scheme'] ) {
 				$port = 80;
-			} else if ( 'https' == $parsed['scheme'] ) {
+			} elseif ( 'https' == $parsed['scheme'] ) {
 				$port = 443;
 			} else {
-				return new Jetpack_Error( 'unknown_scheme_port', "The scheme's port is unknown" );
+				return new WP_Error( 'unknown_scheme_port', "The scheme's port is unknown" );
 			}
 		}
 
-		if ( !ctype_digit( "$timestamp" ) || 10 < strlen( $timestamp ) ) { // If Jetpack is around in 275 years, you can blame mdawaffe for the bug.
-			return new Jetpack_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is malformed.', 'timestamp' ) );
+		if ( ! ctype_digit( "$timestamp" ) || 10 < strlen( $timestamp ) ) { // If Jetpack is around in 275 years, you can blame mdawaffe for the bug.
+			return new WP_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is malformed.', 'timestamp' ) );
 		}
 
 		$local_time = $timestamp - $this->time_diff;
 		if ( $local_time < time() - 600 || $local_time > time() + 300 ) {
-			return new Jetpack_Error( 'invalid_signature', 'The timestamp is too old.' );
+			return new WP_Error( 'invalid_signature', 'The timestamp is too old.' );
 		}
 
 		if ( 12 < strlen( $nonce ) || preg_match( '/[^a-zA-Z0-9]/', $nonce ) ) {
-			return new Jetpack_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is malformed.', 'nonce' ) );
+			return new WP_Error( 'invalid_signature', sprintf( 'The required "%s" parameter is malformed.', 'nonce' ) );
 		}
 
 		$normalized_request_pieces = array(
@@ -202,9 +203,9 @@ function sign_request( $token = '', $timestamp = 0, $nonce = '', $body_hash = ''
 			// Normalized Query String
 		);
 
-		$normalized_request_pieces = array_merge( $normalized_request_pieces, $this->normalized_query_parameters( isset( $parsed['query'] ) ? $parsed['query'] : '' ) );
+		$normalized_request_pieces      = array_merge( $normalized_request_pieces, $this->normalized_query_parameters( isset( $parsed['query'] ) ? $parsed['query'] : '' ) );
 		$flat_normalized_request_pieces = array();
-		foreach ($normalized_request_pieces as $piece) {
+		foreach ( $normalized_request_pieces as $piece ) {
 			if ( is_array( $piece ) ) {
 				foreach ( $piece as $subpiece ) {
 					$flat_normalized_request_pieces[] = $subpiece;
@@ -222,18 +223,19 @@ function sign_request( $token = '', $timestamp = 0, $nonce = '', $body_hash = ''
 
 	function normalized_query_parameters( $query_string ) {
 		parse_str( $query_string, $array );
-		if ( get_magic_quotes_gpc() )
+		if ( get_magic_quotes_gpc() ) {
 			$array = stripslashes_deep( $array );
+		}
 
 		unset( $array['signature'] );
 
 		$names  = array_keys( $array );
 		$values = array_values( $array );
 
-		$names  = array_map( array( $this, 'encode_3986' ), $names  );
+		$names  = array_map( array( $this, 'encode_3986' ), $names );
 		$values = array_map( array( $this, 'encode_3986' ), $values );
 
-		$pairs  = array_map( array( $this, 'join_with_equal_sign' ), $names, $values );
+		$pairs = array_map( array( $this, 'join_with_equal_sign' ), $names, $values );
 
 		sort( $pairs );
 
@@ -260,7 +262,3 @@ function join_with_equal_sign( $name, $value ) {
 		return "{$name}={$value}";
 	}
 }
-
-function jetpack_sha1_base64( $text ) {
-	return base64_encode( sha1( $text, true ) );
-}
diff --git a/packages/connection/src/Manager.php b/packages/connection/src/Manager.php
index 2702adc2d927..85d19400ea8c 100644
--- a/packages/connection/src/Manager.php
+++ b/packages/connection/src/Manager.php
@@ -266,6 +266,14 @@ public function disconnect_site() {
 
 	}
 
+	/**
+	 * @param $text
+	 * @return string
+	 */
+	function sha1_base64( $text ) {
+		return base64_encode( sha1( $text, true ) );
+	}
+
 	/**
 	 * This function mirrors Jetpack_Data::is_usable_domain() in the WPCOM codebase.
 	 *
diff --git a/tests/php/_inc/lib/test_class.rest-api-authentication.php b/tests/php/_inc/lib/test_class.rest-api-authentication.php
index a7d09aa44913..80b6ef8144cf 100644
--- a/tests/php/_inc/lib/test_class.rest-api-authentication.php
+++ b/tests/php/_inc/lib/test_class.rest-api-authentication.php
@@ -1,7 +1,5 @@
 <?php
 
-require_once JETPACK__PLUGIN_DIR . 'class.jetpack-signature.php';
-
 require_once JETPACK__PLUGIN_DIR . '/tests/php/lib/class-wp-test-jetpack-rest-testcase.php';
 require_once JETPACK__PLUGIN_DIR . '/tests/php/lib/class-wp-test-spy-rest-server.php';
 
@@ -196,7 +194,7 @@ public function test_jetpack_rest_api_post_authentication_fail_bad_signature() {
 		$_GET['token'] = 'pretend_this_is_valid:1:' . self::$admin_id;
 		$_GET['timestamp'] = (string) time();
 		$_GET['nonce'] = 'testing123';
-		$_GET['body-hash'] = jetpack_sha1_base64( '{"modules":[]}' );
+		$_GET['body-hash'] = Jetpack::connection()->sha1_base64( '{"modules":[]}' );
 		$_GET['signature'] = 'abc';
 		$this->request = new WP_REST_Request( 'POST', '/jetpack/v4/module/all/active' );
 		$this->request->set_header( 'Content-Type', 'application/json' );
@@ -221,7 +219,7 @@ public function test_jetpack_rest_api_post_authentication_fail_bad_body_hash() {
 			$_GET['token'],
 			$_GET['timestamp'],
 			$_GET['nonce'],
-			jetpack_sha1_base64( '{"modules":[]}' ),
+			Jetpack::connection()->sha1_base64( '{"modules":[]}' ),
 			'GET',
 			'example.org',
 			'80',
@@ -251,7 +249,7 @@ public function test_jetpack_rest_api_post_authentication_success() {
 		$_GET['token'] = 'pretend_this_is_valid:1:' . self::$admin_id;
 		$_GET['timestamp'] = (string) time();
 		$_GET['nonce'] = 'testing123';
-		$_GET['body-hash'] = jetpack_sha1_base64( $body );
+		$_GET['body-hash'] = Jetpack::connection()->sha1_base64( $body );
 		$_GET['signature'] = base64_encode( hash_hmac( 'sha1', implode( "\n", array(
 			$_GET['token'],
 			$_GET['timestamp'],
@@ -291,7 +289,7 @@ public function test_jetpack_rest_api_post_urlencoded_authentication_success() {
 		$_GET['token'] = 'pretend_this_is_valid:1:' . self::$admin_id;
 		$_GET['timestamp'] = (string) time();
 		$_GET['nonce'] = 'testing123';
-		$_GET['body-hash'] = jetpack_sha1_base64( $body );
+		$_GET['body-hash'] = Jetpack::connection()->sha1_base64( $body );
 		$_GET['signature'] = base64_encode( hash_hmac( 'sha1', implode( "\n", array(
 			$_GET['token'],
 			$_GET['timestamp'],
@@ -341,7 +339,7 @@ public function test_jetpack_rest_api_post_multipart_authentication_success() {
 		$_GET['token'] = 'pretend_this_is_valid:1:' . self::$admin_id;
 		$_GET['timestamp'] = (string) time();
 		$_GET['nonce'] = 'testing123';
-		$_GET['body-hash'] = jetpack_sha1_base64( $body );
+		$_GET['body-hash'] = Jetpack::connection()->sha1_base64( $body );
 		$_GET['signature'] = base64_encode( hash_hmac( 'sha1', implode( "\n", array(
 			$_GET['token'],
 			$_GET['timestamp'],