diff --git a/packages/backend/package.json b/packages/backend/package.json
index 5a438d29d6..83256149a2 100644
--- a/packages/backend/package.json
+++ b/packages/backend/package.json
@@ -143,6 +143,7 @@
 		"nanoid": "5.0.6",
 		"nested-property": "4.0.0",
 		"node-fetch": "3.3.2",
+		"node-forge": "1.3.1",
 		"nodemailer": "6.9.12",
 		"nsfwjs": "2.4.2",
 		"oauth": "0.10.0",
@@ -213,6 +214,7 @@
 		"@types/mime-types": "2.1.4",
 		"@types/ms": "0.7.34",
 		"@types/node": "20.11.27",
+		"@types/node-forge": "1.3.11",
 		"@types/nodemailer": "6.4.14",
 		"@types/oauth": "0.9.4",
 		"@types/oauth2orize": "1.11.4",
diff --git a/packages/backend/src/server/api/endpoints/admin/sso/create.ts b/packages/backend/src/server/api/endpoints/admin/sso/create.ts
index 9ebb7b1c80..780fc59e74 100644
--- a/packages/backend/src/server/api/endpoints/admin/sso/create.ts
+++ b/packages/backend/src/server/api/endpoints/admin/sso/create.ts
@@ -125,7 +125,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				name: ps.name ? ps.name : null,
 				type: ps.type,
 				issuer: ps.issuer,
-				audience: ps.audience?.filter(i => !!i),
+				audience: ps.audience?.filter(i => i.length > 0) ?? [],
 				acsUrl: ps.acsUrl,
 				publicKey: publicKey,
 				privateKey: privateKey,
diff --git a/packages/backend/src/server/api/endpoints/admin/sso/list.ts b/packages/backend/src/server/api/endpoints/admin/sso/list.ts
index b67ffec998..e68cfdb73f 100644
--- a/packages/backend/src/server/api/endpoints/admin/sso/list.ts
+++ b/packages/backend/src/server/api/endpoints/admin/sso/list.ts
@@ -48,6 +48,10 @@ export const meta = {
 					type: 'string',
 					optional: false, nullable: false,
 				},
+				useCertificate: {
+					type: 'boolean',
+					optional: false, nullable: false,
+				},
 				publicKey: {
 					type: 'string',
 					optional: false, nullable: false,
@@ -100,6 +104,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				issuer: service.issuer,
 				audience: service.audience,
 				acsUrl: service.acsUrl,
+				useCertificate: service.privateKey != null,
 				publicKey: service.publicKey,
 				signatureAlgorithm: service.signatureAlgorithm,
 				cipherAlgorithm: service.cipherAlgorithm,
diff --git a/packages/backend/src/server/api/endpoints/admin/sso/update.ts b/packages/backend/src/server/api/endpoints/admin/sso/update.ts
index 909f4add6a..c72709f5ee 100644
--- a/packages/backend/src/server/api/endpoints/admin/sso/update.ts
+++ b/packages/backend/src/server/api/endpoints/admin/sso/update.ts
@@ -64,7 +64,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			await this.singleSignOnServiceProviderRepository.update(service.id, {
 				name: ps.name !== '' ? ps.name : null,
 				issuer: ps.issuer,
-				audience: ps.audience?.filter(i => !!i),
+				audience: ps.audience?.filter(i => i.length > 0),
 				acsUrl: ps.acsUrl,
 				publicKey: publicKey,
 				privateKey: privateKey,
diff --git a/packages/backend/src/server/sso/SAMLIdentifyProviderService.ts b/packages/backend/src/server/sso/SAMLIdentifyProviderService.ts
index 4cdc828ab8..fee6e9f74b 100644
--- a/packages/backend/src/server/sso/SAMLIdentifyProviderService.ts
+++ b/packages/backend/src/server/sso/SAMLIdentifyProviderService.ts
@@ -1,5 +1,6 @@
 import { fileURLToPath } from 'node:url';
 import { randomUUID } from 'node:crypto';
+import forge from 'node-forge';
 import * as jose from 'jose';
 import * as Redis from 'ioredis';
 import * as saml from 'samlify';
@@ -55,17 +56,33 @@ export class SAMLIdentifyProviderService {
 	public async createIdPMetadataXml(
 		provider: MiSingleSignOnServiceProvider,
 	): Promise<string> {
-		const today = new Date();
-		const publicKey = await jose
-			.importJWK(JSON.parse(provider.publicKey))
+		const nowTime = new Date();
+		const tenYearsLaterTime = new Date(nowTime.getTime());
+		tenYearsLaterTime.setFullYear(tenYearsLaterTime.getFullYear() + 10);
+		const tenYearsLater = tenYearsLaterTime.toISOString();
+
+		const cert = forge.pki.createCertificate();
+		cert.serialNumber = '01';
+		cert.validity.notBefore = provider.createdAt;
+		cert.validity.notAfter = tenYearsLaterTime;
+		const attrs = [{ name: 'commonName', value: this.config.hostname }];
+		cert.setSubject(attrs);
+		cert.setIssuer(attrs);
+		cert.publicKey = await jose.importJWK(JSON.parse(provider.publicKey))
 			.then(k => jose.exportSPKI(k as jose.KeyLike))
-			.then(k => k.replace(/-----(?:BEGIN|END) PUBLIC KEY-----|\s/g, ''));
+			.then(k => forge.pki.publicKeyFromPem(k));
+		cert.sign(
+			await jose.importJWK(JSON.parse(provider.privateKey ?? '{}'))
+				.then(k => jose.exportPKCS8(k as jose.KeyLike))
+				.then(k => forge.pki.privateKeyFromPem(k)),
+			forge.md.sha256.create(),
+		);
 
 		const nodes = {
 			'md:EntityDescriptor': {
 				'@xmlns:md': 'urn:oasis:names:tc:SAML:2.0:metadata',
 				'@entityID': provider.issuer,
-				'@validUntil': new Date(today.setFullYear(today.getFullYear() + 10)).toISOString(),
+				'@validUntil': tenYearsLater,
 				'md:IDPSSODescriptor': {
 					'@WantAuthnRequestsSigned': provider.wantAuthnRequestsSigned,
 					'@protocolSupportEnumeration': 'urn:oasis:names:tc:SAML:2.0:protocol',
@@ -75,7 +92,7 @@ export class SAMLIdentifyProviderService {
 							'@xmlns:ds': 'http://www.w3.org/2000/09/xmldsig#',
 							'ds:X509Data': {
 								'ds:X509Certificate': {
-									'#text': publicKey,
+									'#text': forge.pki.certificateToPem(cert).replace(/-----(?:BEGIN|END) CERTIFICATE-----|\s/g, ''),
 								},
 							},
 						},
@@ -88,10 +105,6 @@ export class SAMLIdentifyProviderService {
 							'@Binding': 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect',
 							'@Location': `${this.config.url}/sso/saml/${provider.id}`,
 						},
-						{
-							'@Binding': 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST',
-							'@Location': `${this.config.url}/sso/saml/${provider.id}`,
-						},
 					],
 				},
 			},
@@ -105,11 +118,28 @@ export class SAMLIdentifyProviderService {
 	public async createSPMetadataXml(
 		provider: MiSingleSignOnServiceProvider,
 	): Promise<string> {
-		const today = new Date();
-		const publicKey = await jose
-			.importJWK(JSON.parse(provider.publicKey))
+		const nowTime = new Date();
+		const tenYearsLaterTime = new Date(nowTime.getTime());
+		tenYearsLaterTime.setFullYear(tenYearsLaterTime.getFullYear() + 10);
+		const tenYearsLater = tenYearsLaterTime.toISOString();
+
+		const cert = forge.pki.createCertificate();
+		cert.serialNumber = '01';
+		cert.validity.notBefore = provider.createdAt;
+		cert.validity.notAfter = tenYearsLaterTime;
+		const attrs = [{ name: 'commonName', value: this.config.hostname }];
+		cert.setSubject(attrs);
+		cert.setIssuer(attrs);
+		cert.publicKey = await jose.importJWK(JSON.parse(provider.publicKey))
 			.then(k => jose.exportSPKI(k as jose.KeyLike))
-			.then(k => k.replace(/-----(?:BEGIN|END) PUBLIC KEY-----|\s/g, ''));
+			.then(k => forge.pki.publicKeyFromPem(k));
+		cert.sign(
+			await jose.importJWK(JSON.parse(provider.privateKey ?? '{}'))
+				.then(k => jose.exportPKCS8(k as jose.KeyLike))
+				.then(k => forge.pki.privateKeyFromPem(k)),
+			forge.md.sha256.create(),
+		);
+		const x509 = forge.pki.certificateToPem(cert).replace(/-----(?:BEGIN|END) CERTIFICATE-----|\s/g, '');
 
 		const keyDescriptor: unknown[] = [
 			{
@@ -118,7 +148,7 @@ export class SAMLIdentifyProviderService {
 					'@xmlns:ds': 'http://www.w3.org/2000/09/xmldsig#',
 					'ds:X509Data': {
 						'ds:X509Certificate': {
-							'#text': publicKey,
+							'#text': x509,
 						},
 					},
 				},
@@ -132,13 +162,13 @@ export class SAMLIdentifyProviderService {
 					'@xmlns:ds': 'http://www.w3.org/2000/09/xmldsig#',
 					'ds:X509Data': {
 						'ds:X509Certificate': {
-							'#text': publicKey,
+							'#text': x509,
 						},
 					},
 				},
-				'md:EncryptionMethod': {
-					'@Algorithm': 'http://www.w3.org/2001/04/xmlenc#aes256-cbc',
-				},
+				'md:EncryptionMethod': [
+					{ '@Algorithm': `http://www.w3.org/2001/04/xmlenc#${provider.cipherAlgorithm}` },
+				],
 			});
 		}
 
@@ -146,7 +176,7 @@ export class SAMLIdentifyProviderService {
 			'md:EntityDescriptor': {
 				'@xmlns:md': 'urn:oasis:names:tc:SAML:2.0:metadata',
 				'@entityID': provider.issuer,
-				'@validUntil': new Date(today.setFullYear(today.getFullYear() + 10)).toISOString(),
+				'@validUntil': tenYearsLater,
 				'md:SPSSODescriptor': {
 					'@AuthnRequestsSigned': provider.wantAuthnRequestsSigned,
 					'@WantAssertionsSigned': provider.wantAssertionsSigned,
@@ -155,11 +185,13 @@ export class SAMLIdentifyProviderService {
 					'md:NameIDFormat': {
 						'#text': 'urn:oasis:names:tc:SAML:2.0:nameid-format:persistent',
 					},
-					'md:AssertionConsumerService': {
-						'@index': 1,
-						'@Binding': 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST',
-						'@Location': provider.acsUrl,
-					},
+					'md:AssertionConsumerService': [
+						{
+							'@index': 1,
+							'@Binding': 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect',
+							'@Location': provider.acsUrl,
+						},
+					],
 				},
 			},
 		};
@@ -203,7 +235,7 @@ export class SAMLIdentifyProviderService {
 			Body?: { SAMLRequest?: string; RelayState?: string };
 		}>('/:serviceId', async (request, reply) => {
 			const serviceId = request.params.serviceId;
-			const binding = request.query?.SAMLRequest ? 'redirect' : 'post';
+			const binding = 'redirect'; // 今はリダイレクトのみ対応 request.query?.SAMLRequest ? 'redirect' : 'post';
 			const samlRequest = request.query?.SAMLRequest ?? request.body?.SAMLRequest;
 			const relayState = request.query?.RelayState ?? request.body?.RelayState;
 
@@ -236,38 +268,63 @@ export class SAMLIdentifyProviderService {
 				metadata: await this.createIdPMetadataXml(ssoServiceProvider),
 				privateKey: await jose
 					.importJWK(JSON.parse(ssoServiceProvider.privateKey ?? '{}'))
-					.then(k => jose.exportPKCS8(k as jose.KeyLike))
-					.then(k => k.replace(/-----(?:BEGIN|END) PRIVATE KEY-----|\s/g, '')),
+					.then(k => jose.exportPKCS8(k as jose.KeyLike)),
 			});
 
 			const sp = saml.ServiceProvider({
 				metadata: await this.createSPMetadataXml(ssoServiceProvider),
 			});
 
-			const parsed = await idp.parseLoginRequest(sp, binding, { query: request.query, body: request.body });
-			this.#logger.info('Parsed SAML request', { saml: parsed });
+			try {
+				const parsed = await idp.parseLoginRequest(sp, binding, { query: request.query, body: request.body });
+				this.#logger.info('Parsed SAML request', { saml: parsed });
 
-			const transactionId = randomUUID();
-			await this.redisClient.set(
-				`sso:saml:transaction:${transactionId}`,
-				JSON.stringify({
-					serviceId: serviceId,
-					binding: binding,
-					flowResult: parsed,
-					relayState: relayState,
-				}),
-				'EX',
-				60 * 5,
-			);
+				const transactionId = randomUUID();
+				await this.redisClient.set(
+					`sso:saml:transaction:${transactionId}`,
+					JSON.stringify({
+						serviceId: serviceId,
+						binding: binding,
+						flowResult: parsed,
+						relayState: relayState,
+					}),
+					'EX',
+					60 * 5,
+				);
 
-			this.#logger.info(`Rendering authorization page for "${ssoServiceProvider.name ?? ssoServiceProvider.issuer}"`);
+				this.#logger.info(`Rendering authorization page for "${ssoServiceProvider.name ?? ssoServiceProvider.issuer}"`);
 
-			reply.header('Cache-Control', 'no-store');
-			return await reply.view('sso', {
-				transactionId: transactionId,
-				serviceName: ssoServiceProvider.name ?? ssoServiceProvider.issuer,
-				kind: 'saml',
-			});
+				reply.header('Cache-Control', 'no-store');
+				return await reply.view('sso', {
+					transactionId: transactionId,
+					serviceName: ssoServiceProvider.name ?? ssoServiceProvider.issuer,
+					kind: 'saml',
+				});
+			} catch (err) {
+				this.#logger.error('Failed to parse SAML request', { error: err });
+				const traceableError = err as Error & {code?: string};
+
+				if (traceableError.code) {
+					reply.status(500).send({
+						error: {
+							message: traceableError.message,
+							code: traceableError.code,
+							id: 'a8aa8e69-a4c3-4148-8efe-fe3e8cb89684',
+							kind: 'client',
+						},
+					});
+					return;
+				}
+
+				reply.status(400).send({
+					error: {
+						message: 'Invalid SAML Request',
+						code: 'INVALID_SAML_REQUEST',
+						id: '874b9cc2-71cb-4000-95c7-449391ee9861',
+						kind: 'client',
+					},
+				});
+			}
 		});
 
 		fastify.get<{ Params: { serviceId: string } }>(
@@ -371,8 +428,7 @@ export class SAMLIdentifyProviderService {
 					metadata: await this.createIdPMetadataXml(ssoServiceProvider),
 					privateKey: await jose
 						.importJWK(JSON.parse(ssoServiceProvider.privateKey ?? '{}'))
-						.then(k => jose.exportPKCS8(k as jose.KeyLike))
-						.then(k => k.replace(/-----(?:BEGIN|END) PRIVATE KEY-----|\s/g, '')),
+						.then(k => jose.exportPKCS8(k as jose.KeyLike)),
 					loginResponseTemplate: { context: 'ignored' },
 				});
 
@@ -380,7 +436,7 @@ export class SAMLIdentifyProviderService {
 					metadata: await this.createSPMetadataXml(ssoServiceProvider),
 				});
 
-				const samlResponse = await idp.createLoginResponse(
+				const loginResponse = await idp.createLoginResponse(
 					sp,
 					flowResult,
 					binding,
@@ -422,8 +478,7 @@ export class SAMLIdentifyProviderService {
 									},
 									'saml:Subject': {
 										'saml:NameID': {
-											'@Format':
-												'urn:oasis:names:tc:SAML:2.0:nameid-format:persistent',
+											'@Format': 'urn:oasis:names:tc:SAML:2.0:nameid-format:persistent',
 											'#text': user.id,
 										},
 										'saml:SubjectConfirmation': {
@@ -453,8 +508,7 @@ export class SAMLIdentifyProviderService {
 										'@SessionNotOnOrAfter': fiveMinutesLater,
 										'saml:AuthnContext': {
 											'saml:AuthnContextClassRef': {
-												'#text':
-													'urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport',
+												'#text': 'urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport',
 											},
 										},
 									},
@@ -462,8 +516,7 @@ export class SAMLIdentifyProviderService {
 										'saml:Attribute': [
 											{
 												'@Name': 'identityprovider',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': this.config.url,
@@ -471,8 +524,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'uid',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': user.id,
@@ -480,8 +532,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'displayname',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': user.name,
@@ -489,8 +540,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'name',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': user.username,
@@ -498,8 +548,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'preferred_username',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': user.username,
@@ -507,8 +556,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'profile',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': `${this.config.url}/@${user.username}`,
@@ -516,8 +564,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'picture',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': user.avatarUrl,
@@ -525,8 +572,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'mail',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': profile.email,
@@ -534,8 +580,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'email',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:string',
 													'#text': profile.email,
@@ -543,8 +588,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'email_verified',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:boolean',
 													'#text': profile.emailVerified,
@@ -552,8 +596,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'mfa_enabled',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:boolean',
 													'#text': profile.twoFactorEnabled,
@@ -561,8 +604,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'updated_at',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:integer',
 													'#text': Math.floor((user.updatedAt?.getTime() ?? user.createdAt.getTime()) / 1000),
@@ -570,8 +612,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'admin',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:boolean',
 													'#text': isAdministrator,
@@ -579,8 +620,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'moderator',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': {
 													'@xsi:type': 'xs:boolean',
 													'#text': isModerator,
@@ -588,8 +628,7 @@ export class SAMLIdentifyProviderService {
 											},
 											{
 												'@Name': 'roles',
-												'@NameFormat':
-													'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
+												'@NameFormat': 'urn:oasis:names:tc:SAML:2.0:attrname-format:basic',
 												'saml:AttributeValue': [
 													...roles
 														.filter((r) => r.isPublic)
@@ -616,7 +655,7 @@ export class SAMLIdentifyProviderService {
 					relayState,
 				);
 
-				this.#logger.info(`Rendering SAML response page for "${ssoServiceProvider.name ?? ssoServiceProvider.issuer}"`, {
+				this.#logger.info(`Redirecting to "${ssoServiceProvider.acsUrl}"`, {
 					userId: user.id,
 					ssoServiceProvider: ssoServiceProvider.id,
 					acsUrl: ssoServiceProvider.acsUrl,
@@ -624,11 +663,8 @@ export class SAMLIdentifyProviderService {
 				});
 
 				reply.header('Cache-Control', 'no-store');
-				return await reply.view('sso-saml-post', {
-					acsUrl: ssoServiceProvider.acsUrl,
-					samlResponse: samlResponse,
-					relyState: relayState ?? null,
-				});
+				reply.redirect(loginResponse.context);
+				return;
 			} catch (err) {
 				this.#logger.error('Failed to create SAML response', { error: err });
 				const traceableError = err as Error & { code?: string };
diff --git a/packages/backend/src/server/web/views/sso-saml-post.pug b/packages/backend/src/server/web/views/sso-saml-post.pug
deleted file mode 100644
index a3cf7e2391..0000000000
--- a/packages/backend/src/server/web/views/sso-saml-post.pug
+++ /dev/null
@@ -1,21 +0,0 @@
-html
-	body
-		noscript: p
-			| JavaScriptを有効にしてください
-			br
-			| Please turn on your JavaScript
-
-		p
-			| Redirecting...
-
-		form(id='sso', method='post', action=action autocomplete='off')
-			input(type='hidden', name='SAMLResponse', value=samlResponse)
-
-			if relayState !== null
-				input(type='hidden', name='RelayState', value=relayState)
-
-			button(type='submit')
-				| click here if you are not redirected.
-
-		script.
-			document.forms[0].submit();
diff --git a/packages/frontend/src/pages/admin/security.vue b/packages/frontend/src/pages/admin/security.vue
index 5455f25a38..c0be7f91bd 100644
--- a/packages/frontend/src/pages/admin/security.vue
+++ b/packages/frontend/src/pages/admin/security.vue
@@ -427,12 +427,12 @@ function ssoServiceAddNew() {
 		issuer: '',
 		audience: '',
 		acsUrl: '',
+		useCertificate: false,
 		publicKey: '',
 		signatureAlgorithm: 'HS256',
 		cipherAlgorithm: '',
 		wantAuthnRequestsSigned: false,
 		wantAssertionsSigned: true,
-		useCertificate: false,
 		regenerateCertificate: false,
 	});
 }
diff --git a/packages/misskey-js/src/autogen/types.ts b/packages/misskey-js/src/autogen/types.ts
index faaaa4c60d..73c8de605d 100644
--- a/packages/misskey-js/src/autogen/types.ts
+++ b/packages/misskey-js/src/autogen/types.ts
@@ -10488,6 +10488,7 @@ export type operations = {
               issuer: string;
               audience: string[];
               acsUrl: string;
+              useCertificate: boolean;
               publicKey: string;
               signatureAlgorithm: string;
               cipherAlgorithm?: string | null;
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 955f5a11e7..ce245ffb8f 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -295,6 +295,9 @@ importers:
       node-fetch:
         specifier: 3.3.2
         version: 3.3.2
+      node-forge:
+        specifier: 1.3.1
+        version: 1.3.1
       nodemailer:
         specifier: 6.9.12
         version: 6.9.12
@@ -588,6 +591,9 @@ importers:
       '@types/node':
         specifier: 20.11.27
         version: 20.11.27
+      '@types/node-forge':
+        specifier: 1.3.11
+        version: 1.3.11
       '@types/nodemailer':
         specifier: 6.4.14
         version: 6.4.14
@@ -7509,6 +7515,12 @@ packages:
       form-data: 4.0.0
     dev: false
 
+  /@types/node-forge@1.3.11:
+    resolution: {integrity: sha512-FQx220y22OKNTqaByeBGqHWYz4cl94tpcxeFdvBo3wjG6XPBuZ0BNgNZRV5J5TFmmcsJ4IzsLkmGRiQbnYsBEQ==}
+    dependencies:
+      '@types/node': 20.11.27
+    dev: true
+
   /@types/node@18.19.24:
     resolution: {integrity: sha512-eghAz3gnbQbvnHqB+mgB2ZR3aH6RhdEmHGS48BnV75KceQPHqabkxKI0BbUSsqhqy2Ddhc2xD/VAR9ySZd57Lw==}
     dependencies: