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2.8

Cryptography

As a result of the importance of maintaining the confidentiality of the data stored

in the infrastructure of the cloud, we have to talk about the symmetric and asym-

metric cryptographic algorithms as shown in Fig. 5, with the need to an important

mention that the symmetric algorithms are the most important in cloud applica-

tions and services that need encryption due to the greater security force they possess

[32]. Cryptography: is a mix between mathematics and computer science, in which

data are obfuscated and hidden during transfer to be confidential between the two

parties (sender/receiver) and cannot be read by unauthorized people who do not

have key decryption. Cryptography takes into account basic requirements that are

confidentiality, integrity, availability, key management, and non-repudiation.

When we talk about cryptography, it should be mentioned that asymmetric key

algorithms are not efficient enough for small portable devices because they require

more calculations and memory [34], however, there are many protocols that work

according to asymmetric algorithms like SSH, PGP, S/MIME, and SSL/TLS, GPG,

ZRTP, Internet Key Exchange, and SILC. In contrast, symmetric key algorithms are

about 1,000 times faster because they require less math processing capacity. This

is why in our research we chose data encryption using a symmetric key algorithm

because the speed of encoding the data flowing in the cloud is very important. We

chose AES because it is the standard and common algorithm for data encryption

(NIST). It is true that symmetric algorithms are fast in the encryption process, but

their problems are concentrated in: fear of brute force attacks that rely on the use

of symmetric encryption cracking tools so that they depend on the characteristics of

the algorithm to discover the secret key and thus the hack occurred [32]. Therefore,

asymmetric algorithms were used to encrypt the symmetric key algorithm, and as we

know symmetric algorithms are slow but safe because they rely on large mathematical

operations that make their penetration almost impossible and the most common

asymmetric algorithms are: RSA and ECC. But looking at the researches, it turns

out that the ECC algorithm outperforms RSA with operational efficiency, security,

and with fewer parameters and the same key length as 256 recommended by NIST.

ECC is the fastest, most secure, and the lowest memory consumption, so ECC is the

most convenient [35].

Fig. 5 Classification of cryptography algorithms [33]