diff --git a/README.md b/README.md
index 96aea9b0..7909aeec 100644
--- a/README.md
+++ b/README.md
@@ -152,7 +152,7 @@ signature algorithms enabled at same time.
 When signing a xml document you can pass the following options to the `SignedXml` constructor to customize the signature process:
 
 - `privateKey` - **[required]** a `Buffer` or pem encoded `String` containing your private key
-- `publicCert` - **[optional]** a `Buffer` or pem encoded `String` containing your public key
+- `publicCert` - **[optional]** the X.509 certificate to publish in `<KeyInfo>`, or a chain of them, as PEM or as one certificate's base64 without the PEM boundaries, in a `String` or `Buffer`. A value that holds no certificate, such as a public key, produces no `<KeyInfo>`.
 - `signatureAlgorithm` - **[required]** one of the supported [signature algorithms](#signature-algorithms). Ex: `sign.signatureAlgorithm = "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256"`
 - `canonicalizationAlgorithm` - **[required]** one of the supported [canonicalization algorithms](#canonicalization-and-transformation-algorithms). Ex: `sign.canonicalizationAlgorithm = "http://www.w3.org/2001/10/xml-exc-c14n#WithComments"`
 
diff --git a/src/signed-xml.ts b/src/signed-xml.ts
index 66902e71..79ef66dd 100644
--- a/src/signed-xml.ts
+++ b/src/signed-xml.ts
@@ -38,6 +38,20 @@ function findSignatureElements(node: Node): Element[] {
   return signatures.filter(isDomNode.isElementNode);
 }
 
+function certificatesToPublish(publicCert: string): string[] {
+  const certificates = utils.pemCertificates(publicCert);
+  if (certificates.length > 0) {
+    return certificates;
+  }
+
+  try {
+    return [utils.bareCertificate(publicCert)];
+  } catch {
+    // Not a certificate in either form, so there is none to publish, and KeyInfo is optional.
+    return [];
+  }
+}
+
 const warnOriginalXmlWithIds = deprecate(
   () => {},
   "`getOriginalXmlWithIds()` is deprecated and will be removed in a future version. Use the `location` option of `computeSignature()` to place the signature, then `getSignedXml()`. For a detached signature, put an ID attribute the signer recognizes on each referenced element (`wsu:Id` for WS-Security), sign that document, and send it alongside `getSignatureXml()`.",
@@ -229,7 +243,7 @@ export class SignedXml {
     }
 
     // A KeyObject holds a key and never a certificate, so there is no X509Data to build from it.
-    const certificates = typeof publicCert === "string" ? utils.pemCertificates(publicCert) : [];
+    const certificates = typeof publicCert === "string" ? certificatesToPublish(publicCert) : [];
 
     // X509Data requires at least one child: https://www.w3.org/TR/xmldsig-core1/#sec-X509Data
     if (certificates.length === 0) {
diff --git a/src/utils.ts b/src/utils.ts
index 64412736..f449a7c8 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -408,6 +408,19 @@ function pemText(value: string | Buffer): string {
     : value.toString("base64");
 }
 
+// Refuses PEM rather than passing it through as toPem() does, so no key can come out as a certificate.
+export function bareCertificate(value: string): string {
+  const text = normalizePemInput(value);
+  const data = text.replace(/\n/g, "");
+
+  if (!BASE64_TEXT_REGEX.test(text) || !isBase64Data(data)) {
+    throw new Error("Invalid PEM format.");
+  }
+  assertX509Certificate(data);
+
+  return canonicalBase64(data);
+}
+
 /**
  * Returns a value as canonical PEM: one message per certificate or key, wrapped at 64 characters.
  * The value may be a PEM message, several of them, base64 data with the label supplied by the
diff --git a/test/signature-unit-tests.spec.ts b/test/signature-unit-tests.spec.ts
index c6fd483a..7e51e477 100644
--- a/test/signature-unit-tests.spec.ts
+++ b/test/signature-unit-tests.spec.ts
@@ -1442,6 +1442,27 @@ describe("Signature unit tests", function () {
     it("when publicCert is a KeyObject, which holds a key and never a certificate", function () {
       expect(selectKeyInfo({ publicCert: crypto.createPublicKey(privateKey) })).to.be.empty;
     });
+
+    it("when publicCert is a private key", function () {
+      expect(selectKeyInfo({ publicCert: privateKey })).to.be.empty;
+    });
+
+    it("when publicCert is the base64 of a private key, without boundaries", function () {
+      const der = crypto.createPrivateKey(privateKey).export({ type: "pkcs8", format: "der" });
+
+      expect(selectKeyInfo({ publicCert: der.toString("base64") })).to.be.empty;
+    });
+
+    it("when publicCert is the base64 of a certificate with more data after it", function () {
+      const der = fs.readFileSync("./test/static/client_public.der");
+      const publicCert = Buffer.concat([der, Buffer.from("more")]).toString("base64");
+
+      expect(selectKeyInfo({ publicCert })).to.be.empty;
+    });
+
+    it("when publicCert is not a certificate in any form", function () {
+      expect(selectKeyInfo({ publicCert: "not a certificate" })).to.be.empty;
+    });
   });
 
   describe("getCertFromKeyInfo", function () {
@@ -1504,7 +1525,7 @@ describe("Signature unit tests", function () {
     });
   });
 
-  function signWithPublicCert(publicCert: string) {
+  function signWithPublicCert(publicCert: string | Buffer) {
     const sig = new SignedXml({
       privateKey: fs.readFileSync("./test/static/client.pem"),
       publicCert,
@@ -1525,7 +1546,7 @@ describe("Signature unit tests", function () {
   }
 
   // The text of each X509Certificate that signing with this publicCert puts into KeyInfo.
-  function publishedCertificates(publicCert: string): string[] {
+  function publishedCertificates(publicCert: string | Buffer): string[] {
     const doc = new xmldom.DOMParser().parseFromString(signWithPublicCert(publicCert)());
     const certificates = xpath.select("//*[local-name(.)='X509Certificate']", doc);
     isDomNode.assertIsArrayOfNodes(certificates);
@@ -1564,6 +1585,15 @@ describe("Signature unit tests", function () {
     expect(signWithPublicCert(publicCert)).to.throw("Invalid PEM format.");
   });
 
+  it("publishes a publicCert given as the base64 of a certificate, without boundaries", function () {
+    const lines = fs.readFileSync("./test/static/client_public.pem", "latin1").trim().split("\n");
+    const data = lines.slice(1, -1);
+
+    expect(publishedCertificates(data.join(""))).to.deep.equal([data.join("")]);
+    expect(publishedCertificates(data.join("\n"))).to.deep.equal([data.join("")]);
+    expect(publishedCertificates(Buffer.from(data.join("\n")))).to.deep.equal([data.join("")]);
+  });
+
   it("signs a BER certificate into KeyInfo with its octets as given", function () {
     // RFC 7468 section 5.1 allows BER, and XML Signature 1.1 says an implementation SHOULD NOT
     // re-encode a certificate: https://www.w3.org/TR/xmldsig-core1/#sec-X509Data