DV SSL/TLS Certificate for isolierklinker-ackermann.de

Certificate is witin its validity period

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

About the isolierklinker-ackermann.de DV SSL/TLS Certificate

This certificate with serial number ec:09:a0:57:de:6d:59:d6:18:03:b8:93:38:3e:1b:4f for isolierklinker-ackermann.de 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 isolierklinker-ackermann.de 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): ec:09:a0:57:de:6d:59:d6:18:03:b8:93:38:3e:1b:4f
Serial Number (int): 313747789824191551796847679525149875023
Serial Number Length: 128 bits, 16 octets

Subject Key Identifier: 50:3c:20:12:6b:0d:10:78:2d:6c:81:7f:f7:72:2f:eb:37:a4:df:60
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): ba:e0:71:ef:90:ba:e8:29:15:70:00:dd:4e:a1:31:c4:5f:17:c6:03
Fingerprint (SHA-256): 5c:ec:ee:df:6b:3a:fc:40:20:65:5f:ea:2a:13:0d:b9:08:0b:bf:fb:d9:92:3e:89:a2:53:20:89:fe:b4:e6:8a

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

Revocation Information

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

Check the revocation status for certificate isolierklinker-ackermann.de
2
DNS Names
0
Email Addresses
0
IP Addresses

Advanced Certificate Properties

Technical details of the X.509 certificate for isolierklinker-ackermann.de

Public Key Algorithm
RSA
Key Size
2048
Signature Algorithm
SHA256 with RSA
Key Usage
Digital Signature
Key Encipherment
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 isolierklinker-ackermann.de in PEM and ASN.1 format.

Certificate (PEM)

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

Public Key (PEM)

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0oFC/TE5MaUmSCqnFmVn
U+LtEboHdyOnrfz8aPcyMJ5ip7f1W6cB2I0XWFh82oDvuGgSeYCStY9+wHoDCrts
fVDDdmzynPa/ub6dKghFxqL4JRi8jBrnLSNizgSFNx89SzwZTCb3O3Qjm2ttyCy1
07L15h5xfldnvQegxor6+L03nBXMQRgDpvuyaLHmal4697xWqoUIi1SxOHjScHVJ
NWsUtlaIzkdIkMeGNmKzxDjMP2gN0j3mhew1M2Yk2YewdcYjItWIyFDUQmnWu5nT
4mkYx8yPw9cV0QVNTsoNJ5cPJtMVbB2UzsYXWwDr2WHBFHzijznqcg3hctd/vORg
xwIDAQAB
-----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 313747789824191551796847679525149875023
 . . . . . . . . [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 2024-12-18 00:00:00 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2026-01-02 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:19|false] PrintableString 'isolierklinker-ackermann.de'
 . . . . . . . . [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 26573785350933422105255623289742292506807394125557282162438369106541530592376034554091212129258267552282960536632772238914415943140381436898502383583902071242443140575403347735772756679644269370335561134431388514495008597186485988618041744679884379644758440685115973310891111756362588282422117309508919803857089299730758225466094043817859443586516708249838697870716375243946476888427517827575295611045995778253315762055432449726946976440950286956329359194018975560674923937700342128482249502396385574329288351516022485880254275524415375260010167629417357519483332691002829804452683922001596495596338450684034114937031
 . . . . . . . . . . . . . . . . . . . . [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)
							503c20126b0d10782d6c817ff7722feb37a4df60
 . . . . . . . . . . . . . . . . [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 1.3.6.1.4.1.11129.2.4.2
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (366 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (362 bytes)
							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
 . . . . . . . . . . . . . . . . [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 (64 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'isolierklinker-ackermann.de'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.isolierklinker-ackermann.de'
 . . . . [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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