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Che

Metode ale algoritmilor de encriptare ?

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Buna seara !

As vrea sa stiu si eu, in mare, cam ce metode de encriptie exista sau ar putea fi ?

Prima la care ma gandesc:

1) SUBSTITUTIA:

Iei cuvantul PAGINA si inlocuiesti fiecare litera cu alta litera prestabilita (astfel incat sa-l si poti decripta, la nevoie). Si, ar rezulta, de exemplu GBNLXB, dupa modelul:

P = G

A = B

G = N

 I = L

N = X

A = B // deja am mai zis mai sus asta.

2) Mutarea +1 sau +n locuri a fiecarei litere, adica A devine B si B devine C si C devine D, daca e sa le deplasam pe toate cu cate un loc sau A devine C daca e sa le deplasam pe toate cu cate doua (n=2) locuri, ultimele litere luand locul primelor, in alfabet.

3) Transformarea tuturor literelor in numere, apoi faci niste operatii matematice cu ele, apoi le transpui inapoi in litere sau le lasi asa. Iar la decriptare faci operatiile in sens invers.

 

Ce alte metode ar mai fi ? Cum functioneaza criptarea cu parola ?

Care e diferenta intre un hash si o criptare ? Adica stiu ca sunt lucruri diferite, dar cum anume rezulta una si cum anume rezulta cealalta ? Parca este si base64 si criptare dar si hash, ce anume face algoritmul cand genereaza hash-ul ? Masoara dimensiunea fisierului sau pe ce se bazeaza ?

Multumesc anticipat si scuze de intrebari daca par cam de copii dar chiar sunt curios cu aceste lucruri !

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2 hours ago, Che said:

Ce alte metode ar mai fi ? Cum functioneaza criptarea cu parola ?

Care e diferenta intre un hash si o criptare ? Adica stiu ca sunt lucruri diferite, dar cum anume rezulta una si cum anume rezulta cealalta ? Parca este si base64 si criptare dar si hash, ce anume face algoritmul cand genereaza hash-ul ? Masoara dimensiunea fisierului sau pe ce se bazeaza ?

Ai aici cateva informatii de baza despre crypto:

 

 

Encryption vs. Encoding vs. Hashing

 

These are three terms that are commonly mixed. They are not interchangeable and they refer to different things.

 

Encoding is the process of transforming data from one format into another. Converting from Hex to Binary is encoding. The only thing required to read data or to change it into whatever arbitrary format you desire is the encoding scheme. This is a public bit of data that explains how a particular encoding works (e.g. Base64).

 

Encryption is the process of transforming data with the purpose of keeping it secret. This means that the encrypted value will disclose little information about the original data. This process requires an algorithm that can be publicly known and an encryption key that should be kept secret.

 

Hashing is essentially a signature of an arbitrary piece of data. It is a one-way function that cannot be reversed nor can the original information be gleaned from the hash value.

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Symmetric and Asymmetric Encryption

 

Symmetric encryption uses the same key to encrypt and decrypt - e.g. DES, 3DES, AES, etc.

Asymmetric encryption uses a key pair - one for encryption, one for decryption - e.g. RSA.

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Encryption Algorithms

 

DES

symmetric

64-bit block

56-bit key + 8 parity bits

considered insecure

3DES

symmetric

64-bit block

uses 3,2, or 1 keys

3TDEA- Ek1(Dk2(Ek3()))

2TDEA - Ek1(Dk2(Ek1()))

1TDEA - effectively DES - Ek1(Dk1(Ek1()))

AES

symmetric

128-bit block

128, 192, or 256-bit key

AES is a standard based on the Rijndael cipher.

RSA

asymmetric

64/128-bit block

Keys should be 2048+ bits

RSA was never meant to encrypt large amounts of data, so it is not entirely correct to say it is a block cipher.

RC4

symmetric

stream

40-2048 bits

considered insecure

 

Many other encryption algorithms exist. These are just the most common.

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Hashing Algorithms

 

MD5

128-bit hash

considered obsolete. collisions have been identified

SHA-1

160-bit (20 byte) hash

phasing out. collisions have been identified

 

Recommendation is to either use pair of hashing algorithms, or to use SHA-256 or SHA-512.

MD5, SHA-1/256/512 operate on 512-bit blocks.

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Cel mai simplu algoritm de criptare si probabil si cel mai potrivit pentru prietenul tau este inlocuirea unui caracter N cu valoarea lui in ASCII N+x.

 

Sa zicem ca ai cuvantul CAT, iar cheia ta va fi 2. Fiecare dintre litere va fi inlocuita cu valoarea sa in ASCII + 2.

 

Deci CAT devine: ECV.

 

C=67, 67+2=69 (E) samd.

 

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1 hour ago, marcward said:

Cel mai simplu algoritm de criptare si probabil si cel mai potrivit pentru prietenul tau este inlocuirea unui caracter N cu valoarea lui in ASCII N+x.

 

Sa zicem ca ai cuvantul CAT, iar cheia ta va fi 2. Fiecare dintre litere va fi inlocuita cu valoarea sa in ASCII + 2.

 

Deci CAT devine: ECV.

 

C=67, 67+2=69 (E) samd.

 

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A.K.A ROT/Caesar Cipher

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Ai aici ceva interesant despre criptografie, incepe cu Caesar Cipher si termina cu RSA.

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