5: Verifying a Signature Bob receives a message M = "Launch a missile." from Alice, with her signature S. Alice's public key is (e, n). Verify whether the signature is indeed Alice's or not. The public key and signature (hexadecimal) are listed in the following: M = Launch a missile. S = 643D6F34902D9C7EC90CB0B2BCA36C47FA37165C0005CAB026C0542CBDB6802F e = 010001 (this hex value equals to decimal 65537) n = AE1CD4DC432798D933779FBD46C6E1247F0CF1233595113AA51B450F18116115 Suppose that the signature above is corrupted, such that the last byte of the signature changes from 2F to 3F, i.e, there is only one bit of change. Repeat this task, and describe what will happen to the verification process.

Database System Concepts
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ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
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# Verifying a Signature

In this scenario, Bob receives a message M = "Launch a missile." from Alice, along with her signature S. Bob needs to verify whether the signature is indeed from Alice using her public key (e, n).

### Given Data
- **Message (M):** Launch a missile.
- **Signature (S):** 
  ```
  643D6F34902D9C7EC90CB0B2BCA36C47FA37165C0005CAB026C0542CBDD6802F
  ```
- **Public Key:**
  - **e:** 010001 (hexadecimal, equivalent to 65537 in decimal)
  - **n:** 
    ```
    AE1CD4DC432798D933779FBD46C6E1247F0CF1233595113AA51B450F18116115
    ```

### Verification Task
Bob should verify if the signature corresponds to Alice's public key.

### Corrupted Signature Scenario
Suppose the signature is corrupted such that the last byte changes from `2F` to `3F`, introducing a single bit of change. Bob needs to repeat the verification process with this corrupted signature and describe its impact on the verification process.

### Explanation
To verify the original and corrupted signatures, Bob will:
1. **Decrypt the signature** using Alice’s public key (e, n).
2. **Compare the decrypted value** with the hash of the message M.
3. The Single bit change from `2F` to `3F` will likely result in a different decrypted value, causing the verification to fail.

This exercise demonstrates the sensitivity of digital signatures to even minimal corruption, highlighting their importance in ensuring message integrity and authenticity.
Transcribed Image Text:# Verifying a Signature In this scenario, Bob receives a message M = "Launch a missile." from Alice, along with her signature S. Bob needs to verify whether the signature is indeed from Alice using her public key (e, n). ### Given Data - **Message (M):** Launch a missile. - **Signature (S):** ``` 643D6F34902D9C7EC90CB0B2BCA36C47FA37165C0005CAB026C0542CBDD6802F ``` - **Public Key:** - **e:** 010001 (hexadecimal, equivalent to 65537 in decimal) - **n:** ``` AE1CD4DC432798D933779FBD46C6E1247F0CF1233595113AA51B450F18116115 ``` ### Verification Task Bob should verify if the signature corresponds to Alice's public key. ### Corrupted Signature Scenario Suppose the signature is corrupted such that the last byte changes from `2F` to `3F`, introducing a single bit of change. Bob needs to repeat the verification process with this corrupted signature and describe its impact on the verification process. ### Explanation To verify the original and corrupted signatures, Bob will: 1. **Decrypt the signature** using Alice’s public key (e, n). 2. **Compare the decrypted value** with the hash of the message M. 3. The Single bit change from `2F` to `3F` will likely result in a different decrypted value, causing the verification to fail. This exercise demonstrates the sensitivity of digital signatures to even minimal corruption, highlighting their importance in ensuring message integrity and authenticity.
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