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* PUSH NOTE : 3. Symmetric Key Encryption.md

* PUSH NOTE : 03. Symmetric Key Cryptography (2).md

* DELETE FILE : _posts/lecture-notes/modern-cryptography/2023-09-18-symmetric-key-cryptography-2.md
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2024-11-13 11:11:17 +09:00
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@@ -13,6 +13,8 @@ tags:
title: 3. Symmetric Key Encryption title: 3. Symmetric Key Encryption
date: 2023-09-19 date: 2023-09-19
github_title: 2023-09-19-symmetric-key-encryption github_title: 2023-09-19-symmetric-key-encryption
attachment:
folder: assets/img/posts/lecture-notes/internet-security
--- ---
## CPA Security ## CPA Security
@@ -132,7 +134,7 @@ Additional explanation available in [Modes of Operations (Internet Security)](..
### Electronic Codebook Mode (ECB) ### Electronic Codebook Mode (ECB)
![is-03-ecb-encryption.png](../../../assets/img/posts/is-03-ecb-encryption.png) ![is-03-ecb-encryption.png](../../../assets/img/posts/lecture-notes/internet-security/is-03-ecb-encryption.png)
- ECB mode encrypts each block with the same key. - ECB mode encrypts each block with the same key.
- Blocks are independent of each other. - Blocks are independent of each other.
@@ -140,7 +142,7 @@ Additional explanation available in [Modes of Operations (Internet Security)](..
### Ciphertext Block Chain Mode (CBC) ### Ciphertext Block Chain Mode (CBC)
![is-03-cbc-encryption.png](../../../assets/img/posts/is-03-cbc-encryption.png) ![is-03-cbc-encryption.png](../../../assets/img/posts/lecture-notes/internet-security/is-03-cbc-encryption.png)
Let $X = \left\lbrace 0, 1 \right\rbrace^n$ and $E : \mathcal{K} \times X \rightarrow X$ be a **PRP**. Let $X = \left\lbrace 0, 1 \right\rbrace^n$ and $E : \mathcal{K} \times X \rightarrow X$ be a **PRP**.
@@ -172,7 +174,7 @@ Also, CBC mode is not secure if the adversary can predict the IV of the next mes
> m_0' = \mathrm{IV}_2 \oplus \mathrm{IV}_0 \oplus m_0, \quad m_1' = \mathrm{IV}_2 \oplus \mathrm{IV}_1 \oplus m_1 > m_0' = \mathrm{IV}_2 \oplus \mathrm{IV}_0 \oplus m_0, \quad m_1' = \mathrm{IV}_2 \oplus \mathrm{IV}_1 \oplus m_1
> $$ > $$
> >
> and send it to the challenger. > and send it to the challenger.
> 4. In experiment $b$, the adversary will receive $E(k, \mathrm{IV}_b \oplus m_b)$. Compare this with the result of the query from (2). The adversary wins with advantage $1$. > 4. In experiment $b$, the adversary will receive $E(k, \mathrm{IV}_b \oplus m_b)$. Compare this with the result of the query from (2). The adversary wins with advantage $1$.
(More on this to be added) (More on this to be added)
@@ -191,7 +193,7 @@ Note that if $k_1$ is the same as the key used for encrypting messages, then thi
### Counter Mode (CTR) ### Counter Mode (CTR)
![is-03-ctr-encryption.png](../../../assets/img/posts/is-03-ctr-encryption.png) ![is-03-ctr-encryption.png](../../../assets/img/posts/lecture-notes/internet-security/is-03-ctr-encryption.png)
Let $F : \mathcal{K} \times X \rightarrow X$ be a secure **PRF**. Let $F : \mathcal{K} \times X \rightarrow X$ be a secure **PRF**.