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Paŭlo Ebermann
Paŭlo Ebermann
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Requirement of Non Why do block ciphers need a non-Linearitylinear component (Sboxlike an S-box) in Block cipher?

I was not able to articulate why thereWhy is there a requirement of "Non-Linear functions" as a component of many popular block cipherciphers (eg sboxe.g. the S-box in DES or 3DES). how?

How does it make the cipher more secure? 

The only intuition iI have is a non linear function can have many roots (solutions) For eg :. E.g. for a non linear y = F(x)$y = F(x)$, if attacker knows y$y$ to find out the x$x$, there might be many choices which satisfy y= F(x)$y= F(x)$ hence it adds up complexity at attackerattacker's end when ithe tries to make his way back (trace back) from cipher text to Plainplain text.

Any references or detailed material isare appreciated.

Requirement of Non-Linearity (Sbox) in Block cipher

I was not able to articulate why there is a requirement of "Non-Linear functions" as a component of many popular block cipher (eg sbox in DES or 3DES). how does it make the cipher more secure? The only intuition i have is a non linear function can have many roots (solutions) For eg : for a non linear y = F(x) if attacker knows y to find out the x there might be many choices which satisfy y= F(x) hence it adds up complexity at attacker end when it tries to make his way back (trace back) from cipher text to Plain text.

Any references or detailed material is appreciated.

Why do block ciphers need a non-linear component (like an S-box)?

Why is there a requirement of "Non-Linear functions" as a component of many popular block ciphers (e.g. the S-box in DES or 3DES)?

How does it make the cipher more secure? 

The only intuition I have is a non linear function can have many roots (solutions). E.g. for a non linear $y = F(x)$, if attacker knows $y$ to find out the $x$, there might be many choices which satisfy $y= F(x)$ hence it adds up complexity at attacker's end when he tries to make his way back (trace back) from cipher text to plain text.

Any references or detailed material are appreciated.

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David
David
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Requirement of Non-Linearity (Sbox) in Block cipher

I was not able to articulate why there is a requirement of "Non-Linear functions" as a component of many popular block cipher (eg sbox in DES or 3DES). how does it make the cipher more secure? The only intuition i have is a non linear function can have many roots (solutions) For eg : for a non linear y = F(x) if attacker knows y to find out the x there might be many choices which satisfy y= F(x) hence it adds up complexity at attacker end when it tries to make his way back (trace back) from cipher text to Plain text.

Any references or detailed material is appreciated.