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Questions and Answers
What does the digital signature provide in addition to non-repudiation of a message?
How does the verifier verify the sender's digital signature?
What happens if an attacker modifies the data when a digital signature is present?
Why is it essential for users employing Public Key Cryptography (PKC) for encryption to seek digital signatures?
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Which method is more reliable and widely adopted when combining digital signatures with encryption?
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In Knapsack Encryption Algorithm, which knapsack problem is used as the private key?
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What type of sequence is a super increasing knapsack?
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What are the two different keys needed in Public Key Cryptography (PKC)?
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Who developed the Knapsack Encryption Algorithm?
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What is the purpose of using a hard knapsack in the Knapsack Encryption Algorithm?
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Study Notes
Digital Signature and Encryption
- Digital signature provides non-repudiation of message, message authentication, and data integrity.
- Digital signature ensures that sender cannot deny sending the message.
- Digital signature is used in public-key primitives of message authentication.
- Digital signature binds a person/entity to digital data, which can be independently verified by receiver and third party.
Encryption with Digital Signature
- Encryption with digital signature provides confidentiality, authentication, integrity, and non-repudiation.
- There are two methods to combine digital signature with encryption: sign-then-encrypt and encrypt-then-sign.
- Encrypt-then-sign is a more reliable method, where receiver verifies the signature using sender's public key and then decrypts the data using private key.
Knapsack Encryption Algorithm
- Knapsack encryption algorithm is a public key cryptography algorithm developed by Ralph Merkle and Mertin Hellman in 1978.
- It uses two different keys: public key for encryption and private key for decryption.
- Easy knapsack problem is used as private key and hard knapsack problem is used as public key.
Asymmetric Key Algorithm
- Asymmetric key algorithm uses two separate keys for encryption and decryption.
- Public key is used for encryption and private key is used for decryption.
- Advantage of asymmetric key algorithm is easier key distribution and integrity of message.
- Disadvantage of asymmetric key algorithm is slower due to multiple keys.
RSA Algorithm
- RSA algorithm is a public key encryption technique that uses prime numbers for security.
- RSA algorithm has two sets of keys: private key and public key.
- RSA algorithm is used for key exchange, email security, web security, and encryption systems.
Symmetric and Asymmetric Key Cryptography
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Symmetric key cryptography uses the same secret key for encryption and decryption.
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Asymmetric key cryptography uses a pair of keys: public key for encryption and private key for decryption.
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Symmetric key cryptography is faster and more efficient, but it has a key distribution problem.
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Asymmetric key cryptography is more secure, but it is slower and more complex.### Asymmetric Encryption
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Uses public and private keys for encryption and decryption
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Digital signatures verify the validity and credibility of a message, software, or digital record
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Provides proof of origin, identification, and status of an electronic record, transaction, or post
Applications of Asymmetric Encryption
- Encrypted email: uses public key to encrypt a file and private key to decode it
- SSL/TLS cryptographic protocols: provides encrypted connections between websites and browsers
- Bitcoin and other cryptocurrencies: public keys for transactions and private keys for security
- Each unspent transaction output (UTXO) in the Bitcoin ledger is associated with a public key
Advantages of Asymmetric Encryption
- No need to exchange keys, eliminating the key distribution issue
- Improved security: private keys are never exchanged or exposed to others
- Provides digital signatures that can be revoked
- Message verification ensures the sender's authenticity and prevents message alteration
Disadvantages of Asymmetric Encryption
- Slow speed compared to symmetric key encryption
- Authentication of public keys is required to ensure they belong to the intended individual
- Consumes more computer resources than symmetric key encryption
- Loss of a private key can be irreversible
Asymmetric Key Cryptography vs. Symmetric Key Cryptography
- Asymmetric key cryptography uses public and private keys
- Symmetric key cryptography uses a single key for encryption and decryption
- Asymmetric key cryptography is more complex and time-consuming
- Key lengths: symmetric (128 or 256 bits), asymmetric (2048 bits or higher)
Digital Signatures
- Bind a person/entity to digital data
- Use public-key cryptography and a secret key known only to the signer
- Ensure the sender cannot repudiate the origination of the message
- Digital signature scheme based on public key cryptography
Model of Digital Signature
- Each person has a public-private key pair
- Private key is used for signing, and public key is used for verification
- Hash value and signature key produce the digital signature
- Verification algorithm compares the output with the hash value to verify the signature
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Description
Test your knowledge on asymmetric key algorithms, digital signatures, and RSA encryption. Explore the use of public and private keys, encryption, and decryption processes.
