We want to build a block cipher & = (E, D) from two block ciphers &1...

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We want to build a block cipher & = (E, D) from two block ciphers &1 = (E₁, D₁) and E2 = (E2, D2) so that if at some future time one of E₁ or 2 is broken (but not both) then & is still secure. Suppose both & and E2 are defined over (K, X). Define & as: E ((k₁, k2), x):= E1 (k₁, E2 (k2, 2)) and Show that is secure if either E₁ or E2 is secure. D ((k1, k2), y) = D2 (k2, D1 (k1, y)) We want to build a block cipher & = (E, D) from two block ciphers &1 = (E₁, D₁) and E2 = (E2, D2) so that if at some future time one of E₁ or 2 is broken (but not both) then & is still secure. Suppose both & and E2 are defined over (K, X). Define & as: E ((k₁, k2), x):= E1 (k₁, E2 (k2, 2)) and Show that is secure if either E₁ or E2 is secure. D ((k1, k2), y) = D2 (k2, D1 (k1, y))

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To show that is secure if either E1 or E2 is secure we need to demonstrate that any attacker who can ... View the full answer