witraining.org

Issued by Sectigo RSA Domain Validation Secure Server CA

About this certificate

This digital certificate with serial number 02:3e:96:48:37:cb:e0:d7:4a:f0:32:21:bd:4c:2d:84 was issued on by Sectigo Limited.

With 2 subject alternative names this certificate can be used to secure multiple fqdn's. This certificate has already expired and will cause a warning or error message in the browser it's still listed on this site to allow you to look back on previously issued certificates. If we have found any compliance issues with this certificate they will be shown below. I hope this certificate review is providing you the detailed information in a simple form you where looking for.


We have idenified some issues with this certificate:
  • Subscriber Certificate: commonName is deprecated. (BRs: 7.1.4.2.2)

Certificate Subject

CN=witraining.org

Sectigo Limited

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

This certificate has expire since

Certificate Details

Serial Number (hex): 02:3e:96:48:37:cb:e0:d7:4a:f0:32:21:bd:4c:2d:84
Serial Number (int): 2983426479935389099470161939947859332
Serial Number lenght: 122 bits, 16 octets

SubjectKeyId: ee:55:27:ff:ff:92:8c:fb:43:1e:e6:73:67:cf:e0:d8:5d:3e:1e:c8
AuthorityKeyId: 8d:8c:5e:c4:54:ad:8a:e1:77:e9:9b:f9:9b:05:e1:b8:01:8d:61:e1

Fingerprint (sha1): cc:0b:73:d7:bb:7a:a7:3c:cd:0a:c1:0a:8c:ee:df:1f:c7:bb:d1:8e
Fingerprint (sha256): 4e:7f:7f:b2:89:de:8b:38:56:98:b8:e9:96:b6:a4:0f:49:43:1e:75:ba:20:13:be:62:c0:34:82:27:89:65:e9

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

Revocation information

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

Check the revocation status for certificate witraining.org

2

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for witraining.org

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 extensions
No unhandled critical extensions

CA Certificate

This is not a CA certificate

Subject Alternative Names

witraining.org
www.witraining.org

Other certificates including the domain name witraining.org

(limited to 100 certificates)

Certificate

The complete raw certificate details for witraining.org in PEM and ASN.1 format.

Certificate (PEM)

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

Public Key (PEM)

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAxB7ktvZk7g0X3Ymnrtlo
4nMjGl/2l3UA6wDwV+vNs+J9tjOVOmBRuz4lQ1HFuRIciMLjuISyRb6sOt1luEVD
Tz5PSOF2423VNR37/1Y+d2dvCmFKagjjhFisFwsdYP0QsoJGg3SQ55QKhs7yPD1B
nHg/Yf0qEpy82v0WnQjqXIBarazZcTIXfm+UfyuMf92fDeZYOHU1BfGYrqiiEiPk
nJigt7V17mKYdt9JbZxR4XRO2TArzINiNP3g53zrxLeVZa5bvyR26sS7yJxbyGD6
mh3O7URLJu5kFTmxU9cpu7XIV96vmtie1kBBy8pCwD7VcfJ1aLlI8LRHL3WbuEAK
vwIDAQAB
-----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 2983426479935389099470161939947859332
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.2.840.113549.1.1.11 (sha256WithRSAEncryption)
 . . . . . . . . . . . . [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 (countryName)
 . . . . . . . . . . . . . . . . . . . . [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 (stateOrProvinceName)
 . . . . . . . . . . . . . . . . . . . . [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 (localityName)
 . . . . . . . . . . . . . . . . . . . . [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 (organizationName)
 . . . . . . . . . . . . . . . . . . . . [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 (commonName)
 . . . . . . . . . . . . . . . . . . . . [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 2022-02-16 00:00:00 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2023-02-23 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 (commonName)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:19|false] PrintableString 'witraining.org'
 . . . . . . . . [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 (rsaEncryption)
 . . . . . . . . . . . . . . . . [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 24757941884947708260835549465881999455723909804234332805771890380097685379339395305148883579826942853264981744759285397699637214823793755455111841121253375167910848948165522019118477416260503526994882544110577091389222032298843683482659359102517133017551974583311085830012071037872250907169222583930628572110893320645839729630195285698030810168708040117165220173063962366818317981668096516743436971339107675289034634882136277153395987965928613894192773954559213713410840275543499749194544578543296439171289273928632718029690210847329569663493437122079724118876518990076201762557612520081596810880850237165838660537023
 . . . . . . . . . . . . . . . . . . . . [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 (authorityKeyIdentifier)
 . . . . . . . . . . . . . . . . . . . . [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 (subjectKeyIdentifier)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (22 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (20 bytes)
							ee5527ffff928cfb431ee67367cfe0d85d3e1ec8
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.15 (keyUsage)
 . . . . . . . . . . . . . . . . . . . . [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 (basicConstraints)
 . . . . . . . . . . . . . . . . . . . . [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 (extKeyUsage)
 . . . . . . . . . . . . . . . . . . . . [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 (serverAuth)
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.3.2 (clientAuth)
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.32 (certificatePolicies)
 . . . . . . . . . . . . . . . . . . . . [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 (cps)
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [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 (Domain Validation Certificates Policy)
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.1.1 (authorityInfoAccess)
 . . . . . . . . . . . . . . . . . . . . [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 (caIssuers)
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [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 (ocsp)
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [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 (subjectAltName)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (38 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'witraining.org'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.witraining.org'
 . . . . . . . . . . . . . . . . [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 1.2.840.113549.1.1.11 (sha256WithRSAEncryption)
 . . . . . . . . [c:0|t:5|false] NULL 
 . . . . [c:0|t:3|false] BIT STRING (2048 bits)
		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