Prerequisite – RSA Algorithm in Cryptography

**Security of RSA:-**

These are explaied as following below.

**1. Plain text attacks:**

It is classified into 3 subcategories:-

**(i) Short message attack:**

In this we assume that attacker knows some blocks of plain text and tries to decode cipher text with the help of that. So, to prevent this pad the plain text before encrypting.**(ii) Cycling attack:**

In this attacker will think that plain text is converted into cipher text using permutation and he will apply right for conversion. But attacker does not right plain text. Hence will keep doing it.**(iii) Unconcealed Message attack:**

Sometimes happened that plain text is same as cipher text after encryption . So it must be checked it cannot be attacked.

**2. Choosen cipher attack:**

In this attacker is able to find out plain text based on cipher text using Extended Eculedian Algorithm.

**3. Factorisation attack:**

If attacker will able to know P and Q using N, then he could find out value of private key.This can be failed when N contains atleast 300 longer digits in decimal terms, attacker will not able to find. Hence it fails.

**4. Attacks on Encryption key:**

If we take smaller value of E in RSA this may occuR so to avoid this take value of E = 2^16+1 (atleast).

**5. Attacks on Decryption key:**

**(i) Revealed decryption exponent attack:**

If attacker somehow guess decryption key D, not only the cipher text generated by encryption the plain text with corresponding encryption key is in danger, but even future messages are also in danger. So, it is advised to take fresh values of two prime numbers (i.e; P and Q), N and E.**(ii) Low decryption exponent attack:**

If we take smaller value of D in RSA this may occur so to avoid this take value of D = 2^16+1(atleast).

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