covid19.org

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:65:17:52:1c:3d:af:9e:20:83:0f:35:91:03:a6:2a:24:cd was issued on by Let's Encrypt.

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=covid19.org

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:65:17:52:1c:3d:af:9e:20:83:0f:35:91:03:a6:2a:24:cd
Serial Number (int): 295736375439335715526763338750471468360909
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: 1f:b9:3a:e4:f8:41:52:c5:8c:49:02:b0:ac:b4:d5:cf:e5:90:16:18
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 46:eb:37:5d:fb:ef:8b:ff:91:40:70:01:37:6c:d1:8d:93:40:68:50
Fingerprint (sha256): 83:6f:22:60:0f:57:9a:9f:99:58:b3:11:56:41:ff:79:e3:71:27:a4:bf:89:36:91:ad:87:62:d0:85:97:0b:ea

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 covid19.org

2

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for covid19.org

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

*.covid19.org
covid19.org

Other certificates including the domain name covid19.org

(limited to 100 certificates)

Certificate

The complete raw certificate details for covid19.org 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 295736375439335715526763338750471468360909
 . . . . . . . . [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 2020-04-05 07:30:06 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2020-07-04 07:30:06 +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 'covid19.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 (4208 bits)
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:2|false] INTEGER 778605252759419651429928645706732951468084509509921329633719387843291491762980713098350320402584002192466016904647711751730006710222806200518794917848180524532484435170156796244583357373657084074051524319344092803051901294690752348597653643067971524451589862572551790920176833227836108730315331337427564966625354706600701380136553527228902504133763740863887692760520582197343592444556132897717999840583660461256043216344274715054384655258155745963042215622727296285052833067554440342138592150343633080353070632466032347787050877676872710582938577373252934208158463955706346058727683207448547560754846208606233724405419703136411325906034712531347979379731818302876797849826905129433224017276231781290831128830203596810185578724884422855076017827294793072489792394542390646076741630447028749644396010468287210273274810668988156373651281058792202817705857250904788555225953233468828675334554800841667580785236945801469889394835815106677438257963626326447152637468547441393223231087041843726845190310817070089709255007895485954759360051753151985875343896188421938323710354894726270555338379588634299910475665034345729701993962436746421639633939899178606227786951386073706324652952282599851371316232992489243008008010296274672679778541449
 . . . . . . . . . . . . . . . . . . . . [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)
							1fb93ae4f84152c58c4902b0acb4d5cfe5901618
 . . . . . . . . . . . . . . . . [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 (30 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String '*.covid19.org'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'covid19.org'
 . . . . . . . . . . . . . . . . [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)
							00f0007500b21e05cc8ba2cd8a204e8766f92bb98a2520676bdafa70e7b249532def8b905e00000171497611ea000004030046304402204e5403fdcb42d0a1f91453226a32a8691923b438aca3e484594a2c7837757614022042b6538ff688928a4965aa66c36da89c875959365e86c73b96b8755eaeea83b10077005ea773f9df56c0e7b536487dd049e0327a919a0c84a1121284187596817145580000017149761234000004030048304602210082cb07ccd8efff8bde9628cc1b9ed6d22f353564d82c1db8c0bc3fd3f9211269022100e21f28550e213d127c86119337e2f564ab789966e7258acf3264e9a872488272
 . . . . [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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