artedu.cz

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:b5:b8:f6:52:3c:08:d5:22:11:67:63:fe:66:2e:81:3e:6c 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=artedu.cz

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:b5:b8:f6:52:3c:08:d5:22:11:67:63:fe:66:2e:81:3e:6c
Serial Number (int): 323173823132136236707405910294532278271596
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: 43:d9:d7:e7:13:d9:c3:1e:19:b4:b2:18:76:b1:16:f8:e6:66:cb:61
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 84:3b:e2:46:1d:d3:ed:e6:10:1a:da:5b:48:c3:f8:de:93:50:90:74
Fingerprint (sha256): e4:b4:21:47:5f:06:97:cd:2e:4a:e7:c0:04:f8:1b:64:98:67:9e:14:d3:3f:1f:43:c5:32:00:fe:34:59:7b:37

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 artedu.cz

2

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for artedu.cz

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

artedu.cz
www.artedu.cz

Other certificates including the domain name artedu.cz

(limited to 100 certificates)

Certificate

The complete raw certificate details for artedu.cz 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 323173823132136236707405910294532278271596
 . . . . . . . . [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 2020-01-22 14:15:46 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2020-04-21 14:15:46 +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 'artedu.cz'
 . . . . . . . . [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 758068644559714162801729667623156218119384590316636769362108218388071331337260463344810613472164284700361246944539055907429057855222924640328080146048049029573080462974608326936839987346216912679871902683133249267837551121859036344153538187682426455691198198701113411770610815924708297575455415176272693579439385894835405539739402999105683734175568769831238634155348044589473905365668299046648992033960770585589150223765022667992136852317393937517425388118374903092070575151623496731444683109294579992753166716837502874321511509604836492416611102534061059300854203308329168576807215109267233654993286158258122361342465671011334895502700933838016860607585495447494648030157569224843421684164957183240136166559519721775088766099071708547874479235536569483412988155326009835971409516415226314010324669350191310252583037828298303741331218973939917588839729509275864833550854368666962666331624302612880085584351215905416137367178660088915534800935191337473226223430541787729387218022774025150690080356286274000854130208742189458891844214625464886485954746043763934031847271820274114681570750521699008455231123928507947068802171557182699376708962792525508855883872003587172637106888522026016606185955844564672420059350324262564232893476289
 . . . . . . . . . . . . . . . . . . . . [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)
							43d9d7e713d9c31e19b4b21876b116f8e666cb61
 . . . . . . . . . . . . . . . . [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 (28 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'artedu.cz'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.artedu.cz'
 . . . . . . . . . . . . . . . . [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 (247 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (244 bytes)
							00f20077006f5376ac31f03119d89900a45115ff77151c11d902c10029068db2089a37d9130000016fcdd2df79000004030048304602210098091abbbc18e2b8bb1bd84c3919b071c825506fe941282bb5480410865a5293022100948468794148aa851f08c6900e9a5dbbbed242288da0878bcbd8d83629995f3000770007b75c1be57d68fff1b0c61d2315c7bae6577c5794b76aeebc613a1a69d3a21c0000016fcdd2dfb80000040300483046022100e559052d18b81ae16565e3b83cba6c3ffb65d94ca41bc715b63fad7345ecb7c1022100c0be5ce5a24b5ab0125c1bf44f1628da8c92e00ba17d35cf352eea054817aa7a
 . . . . [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)
		00866c25424a409677a73d619e969b89bb67321cbbb39fe256b2057a1e3419061b2b794ec2b66601a41e5519f4893d1e8d951ff131bb7b4d6e3d07d3a479143888127681e9e374134f22a09954ccb8093a2d2527fe7144996338353e87022c7f54f8066b5487c80658be9c5eff39e64b04bf64feb0a2bd3a93a40250a7ac61405a26e695cdeffd52a3d7e8d4368e133accfc083e4f9e98fa989cd88d1c3804f141fd08b829a3c47e5dddcaa24c35c049495e7e7a07be64db494adc8cca2d68ed7646d0429113e7da5144dcc981cf8328537ca6509aa991619c9493c6d8b97ea9478929950087eded5d5061f107fd223b773cf475a967130c1213a9db5fd810a0b2