flashdriveusb.com

Issued by Let's Encrypt Authority X3

About this certificate

This digital certificate with serial number 03:09:ed:0b:8e:50:7b:bb:b8:ae:22:60:dc:1a:db:71:24:96 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=flashdriveusb.com

Let's Encrypt

Organization: Let's Encrypt
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 03:09:ed:0b:8e:50:7b:bb:b8:ae:22:60:dc:1a:db:71:24:96
Serial Number (int): 264714486134314365373166470208975124112534
Serial Number lenght: 138 bits, 18 octets

SubjectKeyId: c6:34:b0:9c:e0:d3:6a:ff:fc:54:e6:66:59:2c:a0:79:1b:a6:37:30
AuthorityKeyId: a8:4a:6a:63:04:7d:dd:ba:e6:d1:39:b7:a6:45:65:ef:f3:a8:ec:a1

Fingerprint (sha1): 9b:68:f1:88:20:4c:9e:81:57:fc:88:83:6c:f9:5b:a4:17:08:ef:de
Fingerprint (sha256): 0f:48:44:48:67:5c:43:43:7d:f4:02:73:5d:2a:a2:67:83:54:a6:a5:dc:b0:be:21:21:01:e6:12:7a:cf:c5:2b

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 flashdriveusb.com

1

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for flashdriveusb.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

flashdriveusb.com

Other certificates including the domain name flashdriveusb.com

(limited to 100 certificates)
flashdriveusb.com
wwwhoaic.com
flashdriveusb.com
flashdriveusb.com
flashdriveusb.com

Certificate

The complete raw certificate details for flashdriveusb.com 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 264714486134314365373166470208975124112534
 . . . . . . . . [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 2019-11-04 18:12:15 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2020-02-02 18:12:15 +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 'flashdriveusb.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 914167602368221630684855411705498470584379315503895111063819108797277442951129451298905822853150630203411794175274031053510561823244783636166808997712782851862716024561549510714666174001565785447208892022948130550103758145502009776107990081121058586104492429989058352451608967045707742288138733805683698766338750108796480937357863089078445952620743714255925981912672977558149964130216725666184622350436853026274187109545491166347137378874297104655289481868222143077594458743914397705356821384722918134542786131389367218338181075769255721836201094148748062826666777981843964531621626008611700714002958833069197183112460250057739897044144281349046886059032939736864248430425586074656295219981626883037075595382919170662001272273150937118775137465986475785997430316824017903895081974115134077799018263102305377829051244169082911816613495686302691762356728239638171689179548461857944963816405348103198980653736835330715527524005704527607263620477029951005144337641708973822393785121901655382211872078527506912236475144736497775983870455830015674736356691624858506847843036849447867261682526685459233536985290499131930386285633714704592794561004438194422071945183218396890907095848894756451837147615818132048320609689656606001870656920673
 . . . . . . . . . . . . . . . . . . . . [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)
							c634b09ce0d36afffc54e666592ca0791ba63730
 . . . . . . . . . . . . . . . . [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 (21 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'flashdriveusb.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 (245 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (242 bytes)
							00f00076005ea773f9df56c0e7b536487dd049e0327a919a0c84a1121284187596817145580000016e37d4fbbe0000040300473045022067cc153fe7b01b825d26ea0a75c558020d40d46495d34619bbbe3569916921b4022100ce5062b4fe96084fd37896c2e76328877a3a74846d04bab1c2c7b53a180be6e300760007b75c1be57d68fff1b0c61d2315c7bae6577c5794b76aeebc613a1a69d3a21c0000016e37d4fc0b0000040300473045022100e2629b3aaf42cefd9cf32efb2d0860ea56fdc5b75c8f4ddcfaffb7090e95b883022052fe16e4b1eeb1890cd270c5b49d6b615dcc53714776eb6b759ab2854a15bf2b
 . . . . [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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