wulingbogor.net

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:90:e9:08:5b:eb:4e:23:ea:52:6f:99:64:9e:5d:d3:59:84 was issued on by Let's Encrypt.

With 3 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=wulingbogor.net

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:90:e9:08:5b:eb:4e:23:ea:52:6f:99:64:9e:5d:d3:59:84
Serial Number (int): 310647272157630707728483568182635057600900
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: 5c:42:8f:5f:42:de:26:cb:4a:fb:29:8b:3f:1e:84:4a:c3:8c:e7:3c
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 61:f4:81:92:da:dc:6c:fb:08:26:05:98:fe:1d:45:6c:00:28:d5:83
Fingerprint (sha256): ef:b4:b5:60:88:1c:a3:e1:9f:54:f5:89:fb:99:60:3f:01:16:57:b8:ee:f9:8e:23:65:f3:c3:6a:b5:e9:65:50

Issuing Certificate URL: http://cert.int-x3.letsencrypt.org/

Revocation information

OCSP Server: http://ocsp.int-x3.letsencrypt.org

Check the revocation status for certificate wulingbogor.net

3

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for wulingbogor.net

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

mail.wulingbogor.net
wulingbogor.net
www.wulingbogor.net

Other certificates including the domain name wulingbogor.net

(limited to 100 certificates)
wulingbogor.net
wulingbogor.net
wulingbogor.net
wulingbogor.net
wulingbogor.net
wulingbogor.net
wulingbogor.net
www.wulingbogor.net
wulingbogor.net
wulingbogor.net
wulingbogor.net
wulingbogor.net

Certificate

The complete raw certificate details for wulingbogor.net in PEM and ASN.1 format.

Certificate (PEM)

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

Public Key (PEM)

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0MS00EV4TRNIa1V++kvq
o1WICFWZNmY5DGfH7eE4xP2F8/1rc4JNekOY0QhiUbxeYXVoqZGj0BN+4jPyxTxn
zLUPQSekQheKJMuskmAiZMFd3OAeDQmke/aM0bFXoddNmp0WxFawoHwpDV2yguYW
WynfzMnqnn7repSZg/QV5utXTCmky8gPFoPvDYXlK3+TFmDbKTfKz72MvL6Swda3
axbVk3HYSfeLXq3Yq29G/OXPyvS286f/64gtXjCLXp6iqZHi89bwghV31sl3Hl58
4/XiWwmKMyBuHYpBbUQh8lwjVciiRF4ir8w/e8gdfmbzs39pT2axvajTVoGhyXA8
ywIDAQAB
-----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 310647272157630707728483568182635057600900
 . . . . . . . . [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 'US'
 . . . . . . . . . . . . [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 'Let's Encrypt'
 . . . . . . . . . . . . [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 'Let's Encrypt Authority X3'
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2018-08-06 16:20:57 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2018-11-04 16:20:57 +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 'wulingbogor.net'
 . . . . . . . . [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 26354566926154757000900032932188321474026592647566227173523100938748162986724402658686075428307064594141541533711205902581151795776105675582467782477009737254468036700970156970614363827205162148276412687934410365426639168435092980091478795646931364879504402261538072072516766952644206548263004335810137479301952397945949794350690631204275410055212353725443872215389995485463333785104090002551460451333277651364871775249293461336750775480129456412436379040101642324937052062936716842642963115600023077219941081442448999101153395847929379808152047665458984011892513626916968159607457504524437075331825231434017672281291
 . . . . . . . . . . . . . . . . . . . . [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 2.5.29.15 (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 2.5.29.37 (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 2.5.29.19 (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 2.5.29.14 (subjectKeyIdentifier)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (22 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (20 bytes)
							5c428f5f42de26cb4afb298b3f1e844ac38ce73c
 . . . . . . . . . . . . . . . . [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 a84a6a63047dddbae6d139b7a64565eff3a8eca1
 . . . . . . . . . . . . . . . . [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 (99 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.48.1 (ocsp)
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:6|false] IA5String 'http://ocsp.int-x3.letsencrypt.org'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [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://cert.int-x3.letsencrypt.org/'
 . . . . . . . . . . . . . . . . [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 (62 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'mail.wulingbogor.net'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'wulingbogor.net'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.wulingbogor.net'
 . . . . . . . . . . . . . . . . [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 (246 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.23.140.1.2.1 (Domain Validation Certificates Policy)
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.4.1.44947.1.1.1
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [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 'http://cps.letsencrypt.org'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.2.2 (unotice)
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:12|false] UTF8String 'This Certificate may only be relied upon by Relying Parties and only in accordance with the Certificate Policy found at https://letsencrypt.org/repository/'
 . . . . . . . . . . . . . . . . [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 (246 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (243 bytes)
							00f10076005581d4c2169036014aea0b9b573c53f0c0e43878702508172fa3aa1d0713d30c00000165104193a8000004030047304502202f7b0c48777da517807d4b20e3aac6601a94923c90bf4b3beb1b9aef8648ba8d022100e8a378b20b534f67aaf358547560eddb78f70272c55c608342b307990309fb07007700293c519654c83965baaa50fc5807d4b76fbf587a2972dca4c30cf4e54547f478000001651041939400000403004830460221008c51474546ff55b4173bb8a1f868ba078c33fff61e06a57d4919e5fd259976e6022100f5d38392fa01683a93a67846b96feef51bd0c32d6f778ae4c215c90d44670365
 . . . . [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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