diff --git a/federation/cryptography/index.test.ts b/federation/cryptography/index.test.ts
index e9056c7..a8fc226 100644
--- a/federation/cryptography/index.test.ts
+++ b/federation/cryptography/index.test.ts
@@ -20,7 +20,7 @@ describe("SignatureValidator", () => {
 
         body = JSON.stringify({ key: "value" });
 
-        const headers = await new SignatureConstructor(
+        const { headers } = await new SignatureConstructor(
             privateKey,
             "https://bob.org/users/6a18f2c3-120e-4949-bda4-2aa4c8264d51",
         ).sign("GET", new URL("https://example.com"), body);
@@ -157,7 +157,7 @@ describe("SignatureConstructor", () => {
     describe("Signing", () => {
         test("should correctly sign ", async () => {
             const url = new URL("https://example.com");
-            headers = await ctor.sign("GET", url, body);
+            headers = (await ctor.sign("GET", url, body)).headers;
             expect(headers.get("Signature")).toBeDefined();
             expect(headers.get("Date")).toBeDefined();
 
@@ -187,7 +187,7 @@ describe("SignatureConstructor", () => {
                 method: "GET",
                 body: body,
             });
-            const newRequest = await ctor.sign(request);
+            const { request: newRequest } = await ctor.sign(request);
 
             headers = newRequest.headers;
             expect(headers.get("Signature")).toBeDefined();
@@ -195,5 +195,12 @@ describe("SignatureConstructor", () => {
 
             expect(await newRequest.text()).toBe(body);
         });
+
+        test("signing should also output a signed string", async () => {
+            const url = new URL("https://example.com");
+            const { signedString } = await ctor.sign("GET", url, body);
+            expect(signedString).toBeString();
+            expect(signedString.length).toBeGreaterThan(10);
+        });
     });
 });
diff --git a/federation/cryptography/index.ts b/federation/cryptography/index.ts
index 7a8d4d7..2add7c8 100644
--- a/federation/cryptography/index.ts
+++ b/federation/cryptography/index.ts
@@ -231,12 +231,15 @@ export class SignatureConstructor {
     /**
      * Signs a request.
      * @param request The request object to sign.
-     * @returns A Promise that resolves to the signed request.
+     * @returns A Promise that resolves to the signed request, plus the signed string.
      * @example
      * const request = new Request();
-     * const signedRequest = await constructor.sign(request);
+     * const { request: signedRequest } = await constructor.sign(request);
      */
-    async sign(request: Request): Promise<Request>;
+    async sign(request: Request): Promise<{
+        request: Request;
+        signedString: string;
+    }>;
 
     /**
      * Signs a request.
@@ -244,41 +247,59 @@ export class SignatureConstructor {
      * @param url The URL object.
      * @param body The request body.
      * @param headers The request headers.
-     * @returns A Promise that resolves to the signed headers.
+     * @param date The date that the request was signed (optional)
+     * @returns A Promise that resolves to the signed headers, and the signed string.
      * @throws TypeError if any required parameters are missing or empty.
      * @example
      * const method = "GET";
      * const url = new URL("https://example.com");
      * const body = "request body";
-     * const signedHeaders = await constructor.sign(method, url, body);
+     * const { headers: signedHeaders } = await constructor.sign(method, url, body);
      */
     async sign(
         method: HttpVerb,
         url: URL,
         body: string,
         headers?: Headers,
-    ): Promise<Headers>;
+        date?: Date,
+    ): Promise<{
+        headers: Headers;
+        signedString: string;
+    }>;
 
     async sign(
         requestOrMethod: Request | HttpVerb,
         url?: URL,
         body?: string,
         headers: Headers = new Headers(),
-    ): Promise<Request | Headers> {
+        date?: Date,
+    ): Promise<
+        | {
+              headers: Headers;
+              signedString: string;
+          }
+        | {
+              request: Request;
+              signedString: string;
+          }
+    > {
         if (requestOrMethod instanceof Request) {
             const request = requestOrMethod.clone();
 
-            const headers = await this.sign(
+            const { headers, signedString } = await this.sign(
                 requestOrMethod.method as HttpVerb,
                 new URL(requestOrMethod.url),
                 await requestOrMethod.text(),
                 requestOrMethod.headers,
+                requestOrMethod.headers.get("Date")
+                    ? new Date(requestOrMethod.headers.get("Date") ?? "")
+                    : undefined,
             );
 
             request.headers.set("Date", headers.get("Date") ?? "");
             request.headers.set("Signature", headers.get("Signature") ?? "");
 
-            return request;
+            return { request, signedString };
         }
 
         if (!url || !body || !headers) {
@@ -287,38 +308,42 @@ export class SignatureConstructor {
             );
         }
 
-        const date = new Date().toISOString();
+        const finalDate = date?.toISOString() ?? new Date().toISOString();
 
         const digest = await crypto.subtle.digest(
             "SHA-256",
             new TextEncoder().encode(body),
         );
 
+        const signedString =
+            `(request-target): ${requestOrMethod.toLowerCase()} ${
+                url.pathname
+            }\n` +
+            `host: ${url.host}\n` +
+            `date: ${finalDate}\n` +
+            `digest: SHA-256=${Buffer.from(new Uint8Array(digest)).toString(
+                "base64",
+            )}\n`;
+
         const signature = await crypto.subtle.sign(
             "Ed25519",
             this.privateKey,
-            new TextEncoder().encode(
-                `(request-target): ${requestOrMethod.toLowerCase()} ${
-                    url.pathname
-                }\n` +
-                    `host: ${url.host}\n` +
-                    `date: ${date}\n` +
-                    `digest: SHA-256=${Buffer.from(
-                        new Uint8Array(digest),
-                    ).toString("base64")}\n`,
-            ),
+            new TextEncoder().encode(signedString),
         );
 
         const signatureBase64 = Buffer.from(new Uint8Array(signature)).toString(
             "base64",
         );
 
-        headers.set("Date", date);
+        headers.set("Date", finalDate);
         headers.set(
             "Signature",
             `keyId="${this.keyId}",algorithm="ed25519",headers="(request-target) host date digest",signature="${signatureBase64}"`,
         );
 
-        return headers;
+        return {
+            headers,
+            signedString,
+        };
     }
 }