71870.com

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:dd:4e:79:fc:98:19:c1:2f:f0:04:b4:f4:ba:b4:0d:b0:73 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=71870.com

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:dd:4e:79:fc:98:19:c1:2f:f0:04:b4:f4:ba:b4:0d:b0:73
Serial Number (int): 336643574059617118014203663727369604935795
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: 52:83:cb:df:8a:8a:e2:44:46:2a:73:e9:44:8b:76:fa:d2:c7:48:54
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 24:6c:72:f1:a9:34:f6:d5:ef:b5:9b:e6:8b:7d:96:cd:7f:39:6c:ab
Fingerprint (sha256): 65:4f:72:86:8d:f1:dc:5b:76:ec:83:53:77:ab:1a:f4:9e:36:f9:86:c9:76:e5:d5:43:22:f1:f8:ea:65:3c:de

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 71870.com

1

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for 71870.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

71870.com

Other certificates including the domain name 71870.com

(limited to 100 certificates)
89474.com
71870.com
canvasmat.com
71870.com
www.71870.com
www.71870.com
89642.com
71870.com
71870.com
www.89490.com
71870.com
www.71870.com
www.71870.com
71870.com
iiaserv.co.za
www.71870.com
incomes.world

Certificate

The complete raw certificate details for 71870.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 336643574059617118014203663727369604935795
 . . . . . . . . [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 2019-07-28 05:30:28 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2019-10-26 05:30:28 +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 '71870.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 891351607719342500266344715230266057828042631889566117667829147684985506017540737526476117448673384006918068804511418833558209709952871748225892944584212649528955428033871952697762792069408849620276196235913458926952072943786208670408695067204218268479236450218059769139569908155925492105787223374938476223195491483031485693795539577230228468285515567157638566484381267256416727243086667521376697336956331067983915903352240683611831656629343784349363154524620739329641152287578804687518989879222440747005414595378235964470886280046004692414681025896363837638097356546151414912486150302916994919611641940753266079267863165558767842161732961710236253106841296833462069319892804233021976443972471860039361898820960422315206900254749218078288178261662250747387945453674566684780482343758644627954695134731476761854000609667759703523460438853583270756375027077627992257701441923485701351017559170815649658868196576646107903812618879057182762780123108744721655294762921564778710204237449946018669753688753467807577345520564735908981760898736579007581375627390509965669256504222119116326008458397554899484387317098551343064604314545073850446607203881300744476993183705710855881494709539458964397792292941993024574563631041998910529094783983
 . . . . . . . . . . . . . . . . . . . . [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)
							5283cbdf8a8ae244462a73e9448b76fad2c74854
 . . . . . . . . . . . . . . . . [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 (13 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String '71870.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 (243 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (240 bytes)
							00ee00750063f2dbcde83bcc2ccf0b728427576b33a48d61778fbd75a638b1c768544bd88d0000016c3745f869000004030046304402200da442f678bc840036f12c0355803644210dd056ba573651ae65d5aaab9b5fca022040bfce6a33ff51703d885c4c752cc6630c28abe4fb34ec4738a5e427cc8d146a007500747eda8331ad331091219cce254f4270c2bffd5e422008c6373579e6107bcc560000016c3745fa490000040300463044022043c09f1dac25cc2920a946a2aef127b4ad8fabe370b5d22623b979ec3f40546c0220173e128e033986e77574041f8d8bd7da9715085cb74dde534679bc03d1150944
 . . . . [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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