markrobson.fr

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:5d:31:76:be:ae:d7:52:dd:27:44:64:ae:3d:e4:6e:57:43 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=markrobson.fr

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:5d:31:76:be:ae:d7:52:dd:27:44:64:ae:3d:e4:6e:57:43
Serial Number (int): 293048866649260949454093507012434924033859
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: 86:40:87:ea:43:00:b8:24:de:9d:28:2e:98:19:78:2d:e2:dd:45:e7
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 72:f1:57:2e:e0:57:e1:6c:ee:51:b4:a9:f6:e7:2d:70:ab:4c:5d:4f
Fingerprint (sha256): 6b:33:55:f3:5f:13:d4:23:fb:ba:53:6d:c5:0e:c5:fe:a0:10:af:51:d9:c8:e7:69:34:87:29:40:b5:fe:6d:b4

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 markrobson.fr

2

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for markrobson.fr

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

8 extensions
No unhandled critical extensions

CA Certificate

This is not a CA certificate

Subject Alternative Names

markrobson.fr
www.markrobson.fr

Other certificates including the domain name markrobson.fr

(limited to 100 certificates)
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
www.markrobson.fr
markrobson.fr
markrobson.fr
www.markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr
markrobson.fr

Certificate

The complete raw certificate details for markrobson.fr 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 293048866649260949454093507012434924033859
 . . . . . . . . [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 2016-07-27 17:35:00 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2016-10-25 17:35:00 +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 'markrobson.fr'
 . . . . . . . . [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 658780838501170630353404623311956084615158420431849869271572450358497365286107923289415819331082937672627942099472169289363729987807215631916264790981787481757274770102881371451382770345264319363180902181124392629351782092655561775171535966608509826627032489817851179445096591409743365725924883047737944915087846116117361809568036638114959753315802729946597977077200057830631253979976204923361508682406147000765869651090557078654710222744246901002778031190615913679549964135701590760028308264342143467258677011138691501106867059928770859838154429947243915496776343102341185467237916663351235017442764082516355002248773429085906838882355803745611334048871662845526047003281117390177433148333536324998262593079276686634126757467210786970713040184992760830731956725142218241336885936290311110025697307543547153544553753797228683996217202994860933573155723125046821637884498727288553086526001840566839534119695128306482462266313051889723623516918117715563714132945946473360498594726040757561311846026658598744789493241625129607812907263297769720403617167418835719329495430033652195330265690658206402237711861066946594729073141417403160026027485481572245549087671233832821413944842447914700981609309567565941052208971538682277073861317489
 . . . . . . . . . . . . . . . . . . . . [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)
							864087ea4300b824de9d282e9819782de2dd45e7
 . . . . . . . . . . . . . . . . [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 (100 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 (36 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'markrobson.fr'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.markrobson.fr'
 . . . . . . . . . . . . . . . . [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 1.2.840.113549.1.1.11 (sha256WithRSAEncryption)
 . . . . . . . . [c:0|t:5|false] NULL 
 . . . . [c:0|t:3|false] BIT STRING (2048 bits)
		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