Background

• Exponentiation based crypto-system (RSA, DH…) often involved division in order to compute :

• Remainder : M mod p
  (for signing M with RSA CRT n= p. q )
• Quotient
• Normalization for modular multiplication

• Side-channel leakage (SPA) may reveal secret bits of exponent in the case of binary exponentiation

  
  

  • In case of division it may reveal quotient bit

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