otpself.hec.co.kr

- Hyundai Engineering Co. Ltd. -

Issued by Thawte SGC CA - G2

About this certificate

This digital certificate with serial number 24:ef:86:06:cd:ac:cf:c2:e6:86:1c:c1:97:c5:2c:15 was issued on by Thawte, Inc..

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:
  • Compliant certificates must not encode explicitTest as an IA5String (RFC 6818: 3)
  • Subscriber Certificate: commonName is deprecated. (BRs: 7.1.4.2.2)
  • Compliant certificates should use the utf8string encoding for explicitText (RFC 6818: 3)
  • Sub certificates SHOULD include Subject Key Identifier in end entity certs (RFC 5280: 4.2 & 4.2.1.2)
  • Subscriber Certificate: extKeyUsage values other than id-kp-serverAuth, id-kp-clientAuth, and id-kp-emailProtection SHOULD NOT be present. (BRs: 7.1.2.3)

Hyundai Engineering Co. Ltd.

Organization: Hyundai Engineering Co. Ltd.
Organization unit: it
State / Province: seoul
Locality: YANGCHEON
Country: KR

Thawte, Inc.

Organization: Thawte, Inc.
Country: US

This certificate has expire since

Certificate Details

Serial Number (hex): 24:ef:86:06:cd:ac:cf:c2:e6:86:1c:c1:97:c5:2c:15
Serial Number (int): 49095885179356003016669432801957063701
Serial Number lenght: 126 bits, 16 octets

SubjectKeyId:
AuthorityKeyId: 24:c0:c0:a4:49:3c:52:0b:12:d8:92:0c:51:d1:87:a7:4d:54:75:2c

Fingerprint (sha1): 9d:64:72:ff:d5:16:b4:da:13:13:f4:81:6e:dd:70:99:84:4c:c0:4d
Fingerprint (sha256): 14:dd:95:5c:a5:9e:e8:59:67:54:fe:6e:2d:45:51:90:3d:d4:1b:0a:18:89:d2:21:a5:b9:6c:16:6d:8f:88:ea

Issuing Certificate URL: http://td.symcb.com/td.crt

Revocation information

OCSP Server: http://td.symcd.com
CRL Distribution Point: http://td.symcb.com/td.crl

Check the revocation status for certificate otpself.hec.co.kr

1

DNS Names

0

Email Addresses

0

IP Addresses

Advanced Certificate Properties

Tehnical certificate details for otpself.hec.co.kr

Public Key Algorithm

RSA

Key Size

2048

Signature Algorithm

SHA1 with RSA

Key Usage

Digital Signature
Key Encipherment

Extended Key Usages

Server Authentication
Client Authentication
Netscape Server-Gated Cryptography

Extensions

8 extensions
No unhandled critical extensions

CA Certificate

This is not a CA certificate

Subject Alternative Names

otpself.hec.co.kr

Other certificates including the domain name hec.co.kr

(limited to 100 certificates)

Certificate

The complete raw certificate details for otpself.hec.co.kr in PEM and ASN.1 format.

Certificate (PEM)

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

Public Key (PEM)

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA06AAEa+AgbJxKVB8RwK7
h9sZgyiDSbEz+P0XfAywwLVlB5n+yNjpDVLZnJEQXIvj7baIIH9To9KPu6rMyl1R
emp28YEAeyblHJjbkunnBwIwrh9v+FplidY3mLqq4pIW40dXBC6pyEvSX1pc0Evd
xsBZi0AJny6y1wu59BRg8unGxNX+PEoxi/r0KTgf13apE1014lUIfHYu5smwt5X1
SvZ1Ma7GeaPwthoH04WKKR1VuoYhH0oaON9MNDy9nT+cgqiBjrg4kf4OrBVwrwuZ
mucJqSv8c3MK25dbm7matkLTMaAxcFOXVU9OTVDUdMCwCxqTeC4fX+XvkrimwZfK
aQIDAQAB
-----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 49095885179356003016669432801957063701
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.2.840.113549.1.1.5 (sha1WithRSAEncryption)
 . . . . . . . . . . . . [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 'Thawte, Inc.'
 . . . . . . . . . . . . [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 'Thawte SGC CA - G2'
 . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2014-08-07 00:00:00 +0000 UTC
 . . . . . . . . . . . . [c:0|t:23|false] UTCTime 2015-10-06 23:59:59 +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 2.5.4.6 (countryName)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:19|false] PrintableString 'KR'
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.8 (stateOrProvinceName)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:19|false] PrintableString 'seoul'
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.7 (localityName)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:20|false] TeletexString, T61String 'YANGCHEON'
 . . . . . . . . . . . . [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:20|false] TeletexString, T61String 'Hyundai Engineering Co. Ltd.'
 . . . . . . . . . . . . [c:0|t:17|true] SET, SET OF 
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.4.11 (organizationalUnitName)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:20|false] TeletexString, T61String 'it'
 . . . . . . . . . . . . [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:20|false] TeletexString, T61String 'otpself.hec.co.kr'
 . . . . . . . . [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 (2160 bits)
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:2|false] INTEGER 26715181421515154210258468266554995210340637022703626743271773671398276395578383421168969414349572488347426897829003368560919906264680020894866139592921529660013902237633384734433976196315058741214717829315793536211087964012175667781183491920439467567594518682274757058321113948478656532819288298497328967213851799612741112802999698770600840421285544195593919690012685825076793381295079503479238105426523542707916609600790542143660855980785525037073888408529893582619687154525966706705726516616395741588573375064687526262572948430869192640561361136684657180506420376996852540768335989607625871645601111391694535248489
 . . . . . . . . . . . . . . . . . . . . [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 2.5.29.17 (subjectAltName)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (21 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:2|false] IA5String 'otpself.hec.co.kr'
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.19 (basicConstraints)
 . . . . . . . . . . . . . . . . . . . . [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 2.5.29.15 (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 2.5.29.32 (certificatePolicies)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (94 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.16.840.1.113733.1.7.54
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [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 'https://d.symcb.com/cps'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.3.6.1.5.5.7.2.2 (unotice)
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:22|false] IA5String 'https://d.symcb.com/rpa'
 . . . . . . . . . . . . . . . . [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 24c0c0a4493c520b12d8920c51d187a74d54752c
 . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 2.5.29.31 (cRLDistributionPoints)
 . . . . . . . . . . . . . . . . . . . . [c:0|t:4|false] OCTET STRING (36 bytes)
 . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:0|true] OtherName 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:0|true] OtherName 
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [c:2|t:6|false] IA5String 'http://td.symcb.com/td.crl'
 . . . . . . . . . . . . . . . . [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 (33 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:6|false] OBJECT IDENTIFIER 2.16.840.1.113730.4.1 (serverGatedCrypto)
 . . . . . . . . . . . . . . . . [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 (75 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://td.symcd.com'
 . . . . . . . . . . . . . . . . . . . . . . . . . . . . [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://td.symcb.com/td.crt'
 . . . . [c:0|t:16|true] SEQUENCE, SEQUENCE OF 
 . . . . . . . . [c:0|t:6|false] OBJECT IDENTIFIER 1.2.840.113549.1.1.5 (sha1WithRSAEncryption)
 . . . . . . . . [c:0|t:5|false] NULL 
 . . . . [c:0|t:3|false] BIT STRING (2048 bits)
		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