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Give the format of X.509 digital certificate and explain the use of a digital signature in it.

written 8.0 years ago by teamques10 ★ 68k

•   modified 4.7 years ago

cryptography and system security

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written 8.0 years ago by teamques10 ★ 68k

• A public key certificate is digitally signed document that is commonly used for authentication and secure exchange of information on open networks.
• A certificate securely binds a public key to the entity that holds the corresponding private key.
• Certificates are digitally signed by the issuing certification authority (CA). They create a trust relationship between two unknown entities.
• Over here the purpose of digital signature is to verify the “issuer of the certificate” i.e. a third-party will use the subject’s public-key provided the digital certificate is issued and signed by a TRUSTED authority
• Consider the following example: An user “Adam” wants to send message to user “Bob”.
• Adam along with the encrypted message he sends will also attach a signature certificate which is issued by a trusted CA. (the whole thing will be hashed)
• Bob will now verify the Signature and check if its issued by a CA (using the CA’s private key) and then decrypt it.

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