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6-11

Miscellaneous

6.6 Keys and Certificates Explained

There are various keys and certificates involved in the process of creat-

ing a DCP. This section tries to shed some light on them and the way

they are used.

6.6.1 What’s a Key

A key is a piece of information (normally a string) that determines the

output of a cryptographic algorithm. The key is used during encryption

by the cryptographic algorithm to transform a certain piece of informa-

tion (e.g. plaintext) to ciphertext, i.e. encrypted information. Vice ver-

sa, during decryption the key is used by the algorithm to decode the

ciphertext back to the original information.

There are two types of keys available:

6.6.2 What’s a Certificate

A certificate is a file that usually contains a key. Additionally it includes

a digital signature to ensure the validity of the key/certificate. With this

the purpose of a certificate is, on the one hand, to provide you with a

key and, on the other, to confirm that this certificate and key belong to

a certain identity (e.g. a person, institute or company).

Ideally the signature comes from a certificate authority (CA) charged

with the task of checking identities before issuing certificates that refer

to this identity. However, the most commonly used certificates are

those that users make for themselves (self-signed certificates). Also

common are certificates that users make for others so that these can

certify validities on behalf of the user (certificate chain, see section

“What’s a Certificate Chain”).

In the DCI Mastering a certificate normally contains a public key

(*.cer or *.pem files). A private key is usually provided in a personal

symmetric If the algorithm uses the same key during en- and

decryption, it is known as a symmetric key algorithm.

asymmetric Algorithms that require two different keys, one for

encryption and one for decryption, are called asym-

metric key algorithms. The concept behind them is

that it is almost impossible to compute one key from

the other. With this you can make one key public

(the public key) while keeping the other in secret (the

private key), thus providing others with the means,

for example, to send encrypted pieces of information

to the private key holder that only he can decode.

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DVS Clipster Guide de l'utilisateur Page 99