Fix typo
Fix typos introduces more
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@@ -82,7 +82,7 @@ The NBT(Next bit test) is complete.
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If $\{X_n\}$ on $\{0,1\}^{l(n)}$ passes NBT, then it's pseudorandom.
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Idea of proof: full proof is on the text.
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Ideas of proof: full proof is on the text.
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Our idea is that we want to create $H^{l(n)}_n=\{X_n\}$ and $H^0_n=\{U_{l(n)}\}$
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@@ -137,7 +137,7 @@ The other part of proof will be your homework, damn.
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If one-way function exists, then Pseudorandom Generator exists.
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Idea of proof:
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Ideas of proof:
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Let $f:\{0,1\}^n\to \{0,1\}^n$ be a strong one-way permutation (bijection).
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@@ -16,7 +16,7 @@ $$
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Pr[x\gets \{0,1\}^n;y=f(x);A(1^n,y)=h(x)]\leq \frac{1}{2}+\epsilon(n)
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$$
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Idea: $f:\{0,1\}^n\to \{0,1\}^*$ is a one-way function.
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Ideas: $f:\{0,1\}^n\to \{0,1\}^*$ is a one-way function.
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Given $y=f(x)$, it is hard to recover $x$. A cannot produce all of $x$ but can know some bits of $x$.
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@@ -46,7 +46,7 @@ $\langle x,1^n\rangle=x_1+x_2+\cdots +x_n\mod 2$
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$\langle x,0^{n-1}1\rangle=x_ n$
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Idea of proof:
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Ideas of proof:
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If A could reliably find $\langle x,1^n\rangle$, with $r$ being completely random, then it could find $x$ too often.
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@@ -123,7 +123,7 @@ $Enc_F(m):$ let $r\gets U_n$; output $(r,F(r)\oplus m)$.
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$Dec_F(m):$ Given $(r,c)$, output $m=F(r)\oplus c$.
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Idea: Adversary sees $r$ but has no idea about $F(r)$. (we choose all outputs at random)
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Ideas: Adversary sees $r$ but has no Ideas about $F(r)$. (we choose all outputs at random)
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If we could do this, this is MMS (multi-message secure).
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@@ -77,7 +77,7 @@ With $g^a,g^b$ no one can compute $g^{ab}$.
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### Public key encryption scheme
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Idea: The recipient Bob distributes opened Bob-locks
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Ideas: The recipient Bob distributes opened Bob-locks
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- Once closed, only Bob can open it.
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@@ -110,7 +110,7 @@ $\{p\gets \tilde{\Pi_n};y\gets Gen_q;a,b,\bold{z}\gets \mathbb{Z}_q:(p,y,y^a,y^b
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So DDH assumption implies discrete logarithm assumption.
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Idea:
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Ideas:
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If one can find $a,b$ from $y^a,y^b$, then one can find $ab$ from $y^{ab}$ and compare to $\bold{z}$ to check whether $y^\bold{z}$ is a valid DDH tuple.
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@@ -28,7 +28,7 @@ This is not more than one-time secure since the adversary can ask oracle for $Si
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We will show it is one-time secure
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Idea of proof:
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Ideas of proof:
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Say their query is $Sign_{sk}(0^n)$ and reveals $pk_0$.
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@@ -104,7 +104,7 @@ One-time secure:
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Then ($Gen',Sign',Ver'$) is one-time secure.
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Idea of Proof:
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Ideas of Proof:
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If the digital signature scheme ($Gen',Sign',Ver'$) is not one-time secure, then there exists an adversary $\mathcal{A}$ which can ask oracle for one signature on $m_1$ and receive $\sigma_1=Sign'_{sk'}(m_1)=Sign_{sk}(h_i(m_1))$.
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