pickus.io

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:ea:87:35:6f:26:04:05:66:64:64:e2:2f:79:5d:b1:4a:f4 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=pickus.io

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:ea:87:35:6f:26:04:05:66:64:64:e2:2f:79:5d:b1:4a:f4
Serial Number (int): 341142654880304187028086853141216984386292
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: 9c:9d:b7:a6:9e:85:d3:18:32:5d:c3:e6:d7:b8:df:ec:27:ce:45:05
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 6a:88:f6:6e:5a:f7:41:6b:36:b4:9b:4c:fd:2e:1d:92:bc:48:a8:8e
Fingerprint (sha256): dc:76:ed:d3:11:8a:fd:ab:b0:ab:30:fd:99:74:32:f3:0f:a6:eb:c2:76:bc:94:f9:6a:d9:66:ac:d6:78:34:86

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 pickus.io

2

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for pickus.io

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

pickus.io
www.pickus.io

Other certificates including the domain name pickus.io

(limited to 100 certificates)

Certificate

The complete raw certificate details for pickus.io 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 341142654880304187028086853141216984386292
 . . . . . . . . [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 2020-02-06 06:00:45 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2020-05-06 06:00:45 +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 'pickus.io'
 . . . . . . . . [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 747336676700494051657585531845983836200148840305647912373222256409856812726958977798896804118641023729070104561219761331049616901134630869297393932948901872547454355210058639982885897098578430098656271686852535669822907424179440212444978013926171604730039454561096386653687494913489145436061914740968182035694703902858826410648644414848772170508230540664859339330891884756072501684516497507602230744811029670335808553026316813529473636788131673157559185267795037067820089112781057074929496600744916045941254902607437024364868678449765607725562453210359826296109697962162973133788027227066256086493614452972157816829729961149119045939173250955103727412564945885715369406212456456512184872372867356550817624676250772780387931024715911097963463716806804951703870899715928285385270909279256698850960536380206538273458083782215984043186599149472802937138352605636311023996604685024163490077391888467163992647338676663036504301751402786641683842482631228598000738291729534804820014255648472561865454517876911564076854980851416886445022950527787399276076037995087898069292342740349622163005966620537920876497910509544718639408792514457254216689776429758635531507817456983126765519720747081117549986185915782891934378870163248152615224570321
 . . . . . . . . . . . . . . . . . . . . [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)
							9c9db7a69e85d318325dc3e6d7b8dfec27ce4505
 . . . . . . . . . . . . . . . . [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 'pickus.io'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.pickus.io'
 . . . . . . . . . . . . . . . . [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)
							00f1007700b21e05cc8ba2cd8a204e8766f92bb98a2520676bdafa70e7b249532def8b905e00000170194d10b70000040300483046022100d057cb39d8449afdf8472e9386f20e12efaaae5c532994ff0ff0e86b567db7b6022100e4b421e45536f687a122d75dcca0e7edba3655f1b948c1f842d2782f78be332c0076006f5376ac31f03119d89900a45115ff77151c11d902c10029068db2089a37d91300000170194d120b0000040300473045022100fedded89b11b13ad95320a4e55d7feb3f406494e55e48d4b58dc6ce7dca2b806022071feef59d3bab0ffbeacc93287c6e9863a4ceac94c5db84a35e6448f62f7453d
 . . . . [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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