www.81951.com

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:cb:ed:98:b9:69:e7:0e:c4:17:02:47:80:39:9d:df:ad:56 was issued on by Let's Encrypt.

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=www.81951.com

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:cb:ed:98:b9:69:e7:0e:c4:17:02:47:80:39:9d:df:ad:56
Serial Number (int): 330729998304991013006409741915265043508566
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: 36:54:36:a7:6a:d8:6e:f7:8c:3c:b3:c1:92:21:61:4b:86:37:0a:d2
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 89:36:9c:84:eb:34:2e:c6:39:14:97:31:94:b3:de:11:27:bd:9e:50
Fingerprint (sha256): bb:cd:40:ee:83:b5:be:71:e3:96:d5:94:ec:83:12:51:eb:be:40:bd:45:00:bd:83:08:7e:2b:94:87:08:6e:23

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 www.81951.com

1

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for www.81951.com

Public Key Algorithm

RSA

Key Size

4096

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

www.81951.com

Other certificates including the domain name 81951.com

(limited to 100 certificates)
www.81951.com
www.81951.com
82951.com
www.81951.com
81951.com
81951.com
81951.com
www.81951.com
81951.com
www.82351.com
81951.com
81951.com
81951.com
www.81951.com
31871.com
artificialtooth.com
www.81951.com

Certificate

The complete raw certificate details for www.81951.com in PEM and ASN.1 format.

Certificate (PEM)

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

Public Key (PEM)

-----BEGIN PUBLIC KEY-----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-----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 330729998304991013006409741915265043508566
 . . . . . . . . [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 2019-06-18 02:42:38 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2019-09-16 02:42:38 +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 'www.81951.com'
 . . . . . . . . [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 (4208 bits)
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:2|false] INTEGER 874153354483991933287960603268730668902886598336152224405442476971427334241188310737261705287802523426656853626973956047604726199252432221373781472310049897760302931676609531638225371164245823779776520585773954728683952868987877021944216991670615140397500996238882363921637950909273876963342858726145835416191876163251557233929330611268590676283804657725280499907224985021582282498875925307182845260618821167168218478137034220800904789174801949880364902065758764107048919016858416044086996617205213409828245976126689045306594167161272839294542098737749879627271693174686232799539912716600649960151979771071346593318862569145899431033933349198393188339923490388776577277075560615488881249410442080431714875118941011473595709384958688176888260862110103196729735205609357206656027908348819849564854705298331602111074222218471983155515801822524062420639129154964179569646117965255767675159897726854959940937737965865597939777562007172812046636216832343794731095158076891844253170563869066473239514201767180725423962040921267612062487337451031725644134364491463509891215058352656844099296575992348278274751756873313939033917504151203304259387538130035079746356366794682124742041352198170708498183888962730281361195542728615306564342758519
 . . . . . . . . . . . . . . . . . . . . [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)
							365436a76ad86ef78c3cb3c19221614b86370ad2
 . . . . . . . . . . . . . . . . [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 (17 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.81951.com'
 . . . . . . . . . . . . . . . . [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 (69 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 1.3.6.1.4.1.11129.2.4.2
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (245 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (242 bytes)
							00f0007600747eda8331ad331091219cce254f4270c2bffd5e422008c6373579e6107bcc560000016b68adf1ef00000403004730450220647a8bab8cab1af4dd4d1a204071eb085f887d7940cfa9cf59486ebc5e588579022100c3397af368e7e21376313b22adeb908f060fa98ff7492d35ae971d5556e8eaac007600293c519654c83965baaa50fc5807d4b76fbf587a2972dca4c30cf4e54547f4780000016b68adf01c0000040300473045022100f6f6479fa32baa56341ba220cc9fd46a3737349c64e18dd71a479d027226d5d602205942cad0bc44585523a06a5bf0f2d9c1c68f8935ad6637fb595906684f890dda
 . . . . [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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