derain.me

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:9a:ae:7a:5f:89:c0:c2:ca:2e:c1:7b:32:22:ec:a6:c4:89 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=derain.me

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:9a:ae:7a:5f:89:c0:c2:ca:2e:c1:7b:32:22:ec:a6:c4:89
Serial Number (int): 313972263370331407143725460776946688771209
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: ff:c5:8f:14:9e:16:43:6d:91:6b:f0:14:f9:fa:e6:63:0a:19:e4:01
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): f3:b9:0c:a3:d4:b8:e6:87:e6:40:58:a0:78:9c:fc:a7:6c:aa:ca:67
Fingerprint (sha256): 0e:a9:fa:7b:c1:3c:f8:5f:d8:49:ea:88:cf:d1:8c:84:3a:a8:cc:8e:6f:c1:f6:95:98:1e:80:78:09:fc:d3:42

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 derain.me

2

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for derain.me

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

derain.me
www.derain.me

Other certificates including the domain name derain.me

(limited to 100 certificates)

Certificate

The complete raw certificate details for derain.me 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 313972263370331407143725460776946688771209
 . . . . . . . . [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 2019-08-29 00:01:30 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2019-11-27 00:01:30 +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 'derain.me'
 . . . . . . . . [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 721050367684732833982891301630767861599328130057378874159007388732180832226299050622482623014992899041651916445260147364027289119583298194975003360782345661970373778704198115327969339696060195105635424888603273244735973933758658402853111107691068246737151362995905407199948353035556375996972452508710655319755299652680433815422272389345121693752869985233005086315441694105223073173915180938685896946539068165667391273428448056461661712370015679350672707053023816304999499910433111559062848982867304387680199858441920077112502349884970580857704641533618713675665676909728345899025765700774910689814739656242529298701553759538803523672043520888334913666224223736103654018557463969004588657856554738498610665165661824157765019613547473454482814383665323457534953977497512506166230325235444412186672570415849478159515177074196177151684462385816656643439135059061960371289953435105400321300917851021954860113523565922980244487695990146517833019232377770444276952261869965256139862152506027050054763384727543311088403304550142715102014478928895757551952891573723474043107837834273344538038828746329163087744785975524753686318252693663324465924973882939407175528808935636831776645525247544678671757013965529523109996963781612142267564033579
 . . . . . . . . . . . . . . . . . . . . [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)
							ffc58f149e16436d916bf014f9fae6630a19e401
 . . . . . . . . . . . . . . . . [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 'derain.me'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.derain.me'
 . . . . . . . . . . . . . . . . [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)
							00f0007700e2694bae26e8e94009e8861bb63b83d43ee7fe7488fba48f2893019dddf1dbfe0000016cdae44d2d0000040300483046022100fcdb32390618f2a5befa9410cfcba6259d7fb238a05c6073eb9645e538506da3022100947d3fc543ecfc00f61c95c51a1bf0c2ad609e45ea923c14645c10029287ef1e00750063f2dbcde83bcc2ccf0b728427576b33a48d61778fbd75a638b1c768544bd88d0000016cdae44d4800000403004630440220209e2ab09ebaca38637eb744cc5f0dd73fa77a061120555cc1981fc0fafe53ea022001ac83b3f9df290022d5b1c9b46f016665672139d316e84c4cec6b24b16f923b
 . . . . [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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