69421.com

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:95:d6:9c:8b:d4:7a:9e:73:52:cb:2e:da:28:e6:77:6d:a8 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=69421.com

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:95:d6:9c:8b:d4:7a:9e:73:52:cb:2e:da:28:e6:77:6d:a8
Serial Number (int): 312324198091997728512509331614913286073768
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: e4:7b:f1:3a:ed:7b:92:71:42:15:40:b4:d2:14:cc:8f:01:17:2f:b8
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): cb:d2:54:2c:97:68:57:bb:54:ea:b2:17:06:ab:89:55:47:c3:ad:dd
Fingerprint (sha256): e7:0d:f0:19:08:51:b7:82:32:74:72:80:8d:d2:d3:73:c0:41:1f:92:2a:22:6b:f8:61:6c:f4:b7:c9:f5:4e:7d

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 69421.com

1

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for 69421.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

69421.com

Other certificates including the domain name 69421.com

(limited to 100 certificates)
www.69421.com
89474.com
www.69421.com
69421.com
bagnaracalabra.org
www.69421.com
www.69421.com
stlouisstemcell.org
69421.com
89642.com
www.69421.com
www.89490.com
69421.com
69421.com
69421.com
69421.com

Certificate

The complete raw certificate details for 69421.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 312324198091997728512509331614913286073768
 . . . . . . . . [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 2020-01-31 20:09:57 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2020-04-30 20:09:57 +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 '69421.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 842730408011559448463185500522449664769604221960411715785264223415996817309488052120586872397967963080175388920417625109910492025571026958159507666974396312205569374347427687122230110144686418904874849956505310488598337960382984595475960874637433002951364113352829455139094259134535546711409277819884842822956274024466618846671832745671888883560421977095898077361906023628003334731571246107796647344998085893230617703021453500217418434522739649860376584433332698106416388014902814772072756789443548739844956949152585936636970367417360643815651846172529049204565644110783449780170146552257605823493639783690529702672083450238054640229860007705934633183027433660898460532293987586555756535186902540796385837344401060694460044733964250696534769958912765127166178321609153822544017897344447248717270853511688477862965255301200747330459161043227348270386915805647576865894482711796401716351296309180686412540008612664251729047849644382219141689926595693687629252804143139371084783221746712668133893875043220832483755583186235909406003810076453632544931464875380130415929520062424890303865370665521162344243119899397109241021434909330604115162137931361454918238968139098417834994029329240664105130884681150178863714014393129536756641996947
 . . . . . . . . . . . . . . . . . . . . [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)
							e47bf13aed7b9271421540b4d214cc8f01172fb8
 . . . . . . . . . . . . . . . . [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 '69421.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 (246 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (243 bytes)
							00f10077005ea773f9df56c0e7b536487dd049e0327a919a0c84a1121284187596817145580000016ffd705faf0000040300483046022100b6b5e63aa669530910eb7d88f65909406fe152aec5c7cd3fda8d62af1ad7d7d0022100f82ee424731f6ca4e8e073cf026311c2cf14d3ff1f65bf53b136c8068d927b9f007600b21e05cc8ba2cd8a204e8766f92bb98a2520676bdafa70e7b249532def8b905e0000016ffd705faf00000403004730450220397c96f959c60c22ac65887e45c9fbb203e56287fadaaf52c5946dbda65eac1e02210086bf474eeff56d9ec99759d6a0d1f39928eb1d5ad63c545383f84e5981b801a2
 . . . . [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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