www.infinityswimmingpools.com

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 04:bf:6e:a9:5c:fa:3a:ad:bd:de:09:91:88:13:53:a1:7a:92 was issued on by Let's Encrypt.

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=www.infinityswimmingpools.com

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 04:bf:6e:a9:5c:fa:3a:ad:bd:de:09:91:88:13:53:a1:7a:92
Serial Number (int): 413590170272452550575768115135036239477394
Serial Number lenght: 139 bits, 18 octets

SubjectKeyId: 0d:08:01:ba:44:40:b6:6d:30:84:41:0a:6b:66:e1:ee:b1:73:8c:95
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 87:a9:2b:a2:1e:ce:ec:b7:4e:d5:ba:27:e3:20:0e:78:3e:63:d0:07
Fingerprint (sha256): 0c:34:f7:aa:31:14:5b:44:66:14:bf:8d:c7:f4:63:81:05:21:0f:eb:e1:91:ba:12:7a:c8:e5:32:cc:56:35:32

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 www.infinityswimmingpools.com

1

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for www.infinityswimmingpools.com

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

www.infinityswimmingpools.com

Other certificates including the domain name infinityswimmingpools.com

(limited to 100 certificates)

Certificate

The complete raw certificate details for www.infinityswimmingpools.com in PEM and ASN.1 format.

Certificate (PEM)

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

Public Key (PEM)

-----BEGIN PUBLIC KEY-----
MIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEAtl5KyEtfmWv24AZCWaLm
FQaleI0qREm5ZB0yf/3hIwnNtBkS77+8xNYHg9SpXDfyirfBeJClkruqoi1McRGu
+4NMkdRyWXHrd/y4/BkPCs0X6c6GjbMmo5eF4kAsCvliC2u9XaNCLVBdsWImTaxV
xxFXx6ITMVmWvdnnc0YQutVIIqBGZDS17McGevVW+IdDZZPMPxYYaYYkvyFbq+TC
e+YAB7mUR7F47CRtdfqsuLH5GBbwcA38dM7WBB//OM9ADUtRFzs2lgADiWy9JwVq
xkOrleGKFVLEmHxQSXLy686DIkIq1sDD3drmASk+UQxE/yS6tHE+NBJm3TibAW1a
f+sI4vkvuiM8C5gSI9qvOTwzWwY1UQuy5bfBeJ909BoNsZ0250PuY17b4j6PF/ZN
Mav4m0K6+8cmBefDoxoa6mrYYwjYKYrlrZpdbG9m97jUVf6dfsxugatcJn4tCJEB
5CJavC9GK21bGPmd3Z3EOstXxCu6De38r2yQEEhD0Ozb1k2J8AGLveBqt30fiHw1
glN16Ia98p7zhk26lb/xNyn7W9WpKXHR11y07d6MhcTcvkQba7WmRyIumt0lBxdf
pQh891fdOjyn6WzhkWo7IWopmeefTmuXSBeUqhDEw88EYbNRkGS8RBWbboxrsi+c
oAzXZCgg1C6ZQjs0gaDYPW0CAwEAAQ==
-----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 413590170272452550575768115135036239477394
 . . . . . . . . [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 2020-01-16 06:32:08 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2020-04-15 06:32:08 +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 'www.infinityswimmingpools.com'
 . . . . . . . . [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 743997869922324037991590370530259451295039218609731835899827106786098633182159855559436127945586841168192254578710492189880901381072221805142882869456460556203403702830817023573849309015236613392819567950061797965809627101496375373871111346793464526113878242588416903157056138523831429298579333577642821232041861213912084655621830323023985404056322379367665126947546923934737222130951064708547042467798685927139790738130425624763322585555262875814433200162965293112648566182734725164422941764718162778868872131909267382850599140481863667500244181035676762800274295677444590138799216916237508794604439737291646034863831802720281360029469536534749390238261531589025619546050881420042443219984849808315035030209242327086629147807856834575244944039686186385568791537527003748252757304240505968238909109387585924575793269660779110659611164535625938130870413156216285230023836805348684638793107029889403738975744931986040620936980762977795236031419981918463331146871720575245581744754641853808898671539943430500517747418381041813452627125107566367788959783189463496422036360263094286841060479692480343925880808994253692120919597177132659193505596726394190521149021569403518851382421944037581657295038514552055616927758855006996812659178861
 . . . . . . . . . . . . . . . . . . . . [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)
							0d0801ba4440b66d3084410a6b66e1eeb1738c95
 . . . . . . . . . . . . . . . . [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 (33 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'www.infinityswimmingpools.com'
 . . . . . . . . . . . . . . . . [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 (244 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (241 bytes)
							00ef0076005ea773f9df56c0e7b536487dd049e0327a919a0c84a1121284187596817145580000016fad443f690000040300473045022044d6a52a95766d7737f1554686e8306ba9d0c4ed7572ad001e8c57ed28a0240b022100fdfc44e6442ccbffa6e4e5f5379a404bee9477d3f034518a2d9ab90ecb1f21ea00750007b75c1be57d68fff1b0c61d2315c7bae6577c5794b76aeebc613a1a69d3a21c0000016fad443f8b000004030046304402205e7e90f8181aafe5dbf7653c8f6e9d7f09a6aedc525b5e2e9f43fbfe21b1af34022035ab79ad8371c8d2cea8039175a7eb4475541e7f777a85a40e7ba6a179cc9dea
 . . . . [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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