
Revista Innovación y Software
Vol. 6, No. 2, Mes Septiembre - Febrero, 2025
ISSN: 2708-0935
Pág. 134-158
https://revistas.ulasalle.edu.pe/innosoft
same output [8]. Symmetric encryption algorithms, they use a single secret key, while asymmetric encryption
algorithms use a pair of keys, one private and one public [8]. Data encryption refers to the conversion of plaintext
into ciphertext, whereas data decryption is the reverse process [8–10,14,18]. Asymmetric algorithms like RSA
(Rivest-Shamir-Adleman) [3,5,6,8,13,14,19–27], ECC [5,6,8,19–23,28–31], and ElGamal [13,19–21], they
use asymmetric key cryptography, which involves a pair of keys - private and public. Dynamic encryption has
shown promising results in recent research [5,8,11], when applied to asymmetric algorithms. Since asymmetric
algorithms are not within the scope of this work, they are not examined here and could be considered for
future works. There are also various symmetric key cryptography algorithms, such as DES (Data Encryption
Standard) [3,13,14,22,23,27,32,33], 3DES or TripleDES (Triple Data Encryption Standard) [14,21–23,34],
Blowfish [22,23,35–38], Salsa20 [38,39], and AES (Advanced Encryption Standard) [13,21–23,26,27,40,41],
to mention a few. In this research, the AES-256 version [38,40,41], it has been employed. In reference [22], it
is noted that AES is a symmetric block cipher that can operate with different block sizes and supports key
lengths of 128, 192, and 256 bits. DES processes 64 bits of plaintext to produce 64 bits of ciphertext, using a
series of substitution and permutation rounds, and decryption is achieved by reversing the encryption process.
Due to the limited key size of 64 bits, DES is considered insecure for modern standards. To improve security,
3DES was developed as a more robust alternative. Another symmetric algorithm, Blowfish, employs a variable-
length block cipher with key lengths spanning from 32 to 448 bits [22,23]. Although Blowfish is versatile, it
is often used with a block size of 64 bits. Regarding the symmetric algorithm Salsa20 [39], it is ChaCha20’s
predecessor. Both algorithms are not block-cipher because they work with keystream generation. According
to [39], Salsa20 is addition/rotation/XOR (ARX)–based cryptographic primitive. Their keystream generation
algorithm comprises three simple operations: Addition modulo 232 (⊞), constant distance left bit rotation
(n), and bitwise XOR operation. These operations are swift in any circuit, and hence the cipher can achieve
significant speed with a high security margin. The Salsa20 cipher takes a 256-bit key (k), a 128-bit constant
(c), and a 128-bit initial vector (v), or IV, and generates a 512-bit keystream. The key is divided into eight
32-bit words (k0, k1, . . . , k7). Similarly, the constant and the IV are also broken into 32-bit words (c0, c1, c2, c3)
and (v0, v1, t0, t1). Due to the use of the 256-bit key, the cipher is also called 256-bit Salsa20. In the original
Salsa20 cipher, the number of rounds is 20. After the final round, the initial state Xis added modulo (232) to
the updated state X20 word-by-word, and the keystream (Z) of 512 bits is achieved, that is, Z=X⊞X20. This
keystream is then bitwise XORed to plaintext to get the ciphertext. Besides, the Salsa20 scheme, it is commonly
generated a 512-bit keystream. This proposal is appealing for encryption due to its high speed and security. Due
to their efficient algorithm and fast performance, it has been attracted by cryptographic analysis since their
release [39]. Some research [5,8], they have revealed that symmetric encryption algorithms, they have reported
static ciphertext results. Despite that it does not mean, in all cases that they are vulnerable schemes [5].
However, there exists some standard encryption alternatives that they have been threatened by quantum
computing [8,22,23,42]. In contrast to some views, other researchers [43–45], they emphasize that the AES and
Facultad de Ingeniería
Universidad La Salle, Arequipa, Perú
facin.innosoft@ulasalle.edu.pe
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