DV SSL/TLS Certificate for *.operaduomo.firenze.it

Certificate is witin its validity period

Issued by Sectigo Limited (Sectigo RSA Domain Validation Secure Server CA)

About the *.operaduomo.firenze.it DV SSL/TLS Certificate

This certificate with serial number 1b:7b:f3:ca:bb:6a:c6:10:85:fc:9f:fd:a4:8f:be:3b for *.operaduomo.firenze.it was issued on by Sectigo Limited.

With 2 subject alternative names, this certificate can be used to secure multiple FQDNs. This DV SSL/TLS Certificate is currently within its validity period but we haven't checked the revocation status of this certificate, you can do this simply on revocationcheck.com. We have found some issues with the compliance of this certificate, they are be shown below. We hope this DV SSL/TLS Certificate review for *.operaduomo.firenze.it provides you with the detailed information you were looking for.


We have identified some issues with this certificate:
  • Subscriber certificates use of Subject Key Identifier is NOT RECOMMENDED (BRs v2: 7.1.2.7.6)
  • Subscriber Certificate: commonName is NOT RECOMMENDED. (BRs: 7.1.2.7.1)

Sectigo Limited

Organization: Sectigo Limited
State / Province: Greater Manchester
Locality: Salford
Country: GB

This X.509 certificate will expire on

Certificate Details

Serial Number (hex): 1b:7b:f3:ca:bb:6a:c6:10:85:fc:9f:fd:a4:8f:be:3b
Serial Number (int): 36532753087417805910858214280073821755
Serial Number Length: 125 bits, 16 octets

Subject Key Identifier: c1:02:ee:2d:bd:2d:17:42:db:ca:d2:cc:9e:3f:1a:12:da:e7:d0:b5
Authority Key Identifier: 8d:8c:5e:c4:54:ad:8a:e1:77:e9:9b:f9:9b:05:e1:b8:01:8d:61:e1

Fingerprint (SHA-1): 4e:48:c2:b4:a6:3b:74:a4:a2:96:06:24:f2:34:55:8d:cd:1d:ec:b6
Fingerprint (SHA-256): f9:c5:74:5b:57:a1:df:fd:c3:d2:ad:ef:a7:2d:61:0a:a8:ba:bb:cc:65:1a:58:20:5d:9d:d6:cc:fb:2d:aa:f8

Issuing Certificate URL: http://crt.sectigo.com/SectigoRSADomainValidationSecureServerCA.crt

Revocation Information

OCSP Server: http://ocsp.sectigo.com

Check the revocation status for certificate *.operaduomo.firenze.it
2
DNS Names
0
Email Addresses
0
IP Addresses

Advanced Certificate Properties

Technical details of the X.509 certificate for *.operaduomo.firenze.it

Public Key Algorithm
RSA
Key Size
2048
Signature Algorithm
SHA256 with RSA
Key Usage
Key Encipherment
Digital Signature
Extended Key Usages
Server Authentication
Client Authentication
Extensions
9
CA Certificate
This is not a CA certificate

Subject Alternative Names

X.509 Certificate

The complete raw X.509 certificate details for *.operaduomo.firenze.it in PEM and ASN.1 format.

Certificate (PEM)

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

Public Key (PEM)

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA9yPfCM9ZiOaMe2pZSGCy
cfjdjYtW2AZkUAUrG9ssx6TjzArCYE17VTISx0ph5hYy3hf0bWsdrP+nkr6PLb3g
bX6Y58PJXaYPuK57bv4YjcXFCnGYKxXBIHIK9g8CG/jGu/F0qb7uwpsysPqUmTCn
jOO/1/YivR6PO5nTZQ4Hwl7h/TooYQFucWzj+LN4Jy1awapDOVX4LbsX4o5rlbOm
Bsl02QHeQaddqHQdGdZPohJsOu0edqPeV+Yy/ZwhCNcOCshVJORx02EM/XnNAp88
j1QyDYRw3wE65Cr74UTm/ApUhKzUmDR1RPJdiGRa9QXN71NiSIpiFGeRbHSZBzDx
AQIDAQAB
-----END PUBLIC KEY-----

ASN.1 Decoded

 [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . [c:2|t:0|true] OtherName 
 . . . . . . . . . . . . [c:0|t:2|false] INTEGER 2
 . . . . . . . . [c:0|t:2|false] INTEGER 36532753087417805910858214280073821755
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.2.840.113549.1.1.11
 . . . . . . . . . . . . [c:0|t:5|false] NULL []
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.6
 . . . . . . . . . . . . . . . . . . . . [c:0|t:19|false] PrintableString 'GB'
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.8
 . . . . . . . . . . . . . . . . . . . . [c:0|t:19|false] PrintableString 'Greater Manchester'
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.7
 . . . . . . . . . . . . . . . . . . . . [c:0|t:19|false] PrintableString 'Salford'
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.10
 . . . . . . . . . . . . . . . . . . . . [c:0|t:19|false] PrintableString 'Sectigo Limited'
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.3
 . . . . . . . . . . . . . . . . . . . . [c:0|t:19|false] PrintableString 'Sectigo RSA Domain Validation Secure Server CA'
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2024-10-07 00:00:00 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2025-11-07 23:59:59 +0000 UTC
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.3
 . . . . . . . . . . . . . . . . . . . . [c:0|t:12|false] UTF8String '*.operaduomo.firenze.it'
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.2.840.113549.1.1.1
 . . . . . . . . . . . . . . . . [c:0|t:5|false] NULL []
 . . . . . . . . . . . . [c:0|t:3|false] BIT STRING (2160 bits)
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:2|false] INTEGER 31198550088500886439432822541530116525471614745734867717921658812204628665424329713676219718535517568485272321995848888186736139834282153291006466700345942066126589615966080711822484381629393237451703541918930489809898738465593312293862171451127115779522105696649739726621008442300260888386541785126308365605032088932007044969774265759705256414257244546641694429667382913014660065970501170626972549076032242255828322421571099335397745893362874968266362204312924958763767398478666153532347527449678409213201748712000589883045057462143097858434265006565505994618748763090292031317291429249831985480612660084983702024449
 . . . . . . . . . . . . . . . . . . . . [c:0|t:2|false] INTEGER 65537

 . . . . . . . . [c:2|t:3|true] ORAddress 
 . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.35
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (24 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:0|false] OtherName 8d8c5ec454ad8ae177e99bf99b05e1b8018d61e1
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.14
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (22 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (20 bytes)
							c102ee2dbd2d1742dbcad2cc9e3f1a12dae7d0b5
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.15
 . . . . . . . . . . . . . . . . . . . . [c:0|t:1|false] BOOLEAN true
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (4 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:3|false] BIT STRING (3 bits)
							05a0
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.19
 . . . . . . . . . . . . . . . . . . . . [c:0|t:1|false] BOOLEAN true
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (2 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.37
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (22 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.3.1
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.3.2
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.32
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (66 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.4.1.6449.1.2.2.7
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.2.1
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:22|false] IA5String 'https://sectigo.com/CPS'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.23.140.1.2.1
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.1.1
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (120 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.48.2
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:6|false] IA5String 'http://crt.sectigo.com/SectigoRSADomainValidationSecureServerCA.crt'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.48.1
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:6|false] IA5String 'http://ocsp.sectigo.com'
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.17
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (50 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String '*.operaduomo.firenze.it'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'operaduomo.firenze.it'
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.4.1.11129.2.4.2
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (364 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (360 bytes)
							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
 . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.2.840.113549.1.1.11
 . . . . . . . . [c:0|t:5|false] NULL []
 . . . . [c:0|t:3|false] BIT STRING (2048 bits)
		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