Digital Signature Verification with RSA Algorithm

# Verifying a Digital Signature with RSA Algorithm

### Question

What is needed to verify a digital signature that was created using an RSA algorithm?

### Explanations

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A. B. C. D.

A.

To verify a digital signature created using an RSA algorithm, the verifier needs the public key of the signer, which can be used to verify the authenticity of the signature.

RSA is a widely used public-key cryptosystem that relies on the mathematical properties of prime numbers to create a pair of keys: a public key and a private key. The public key can be freely distributed, while the private key must be kept secret by the owner.

To create a digital signature using RSA, the signer uses their private key to encrypt a hash of the message being signed. The resulting signature can be decrypted by anyone who has the signer's public key, which can be used to verify that the message was indeed signed by the owner of the private key.

Therefore, the answer to this question is A. public key. The public key is needed to verify the signature, as it allows the verifier to decrypt the signature and compare it to the hash of the original message.

In contrast, the private key is used by the signer to create the signature, and it should be kept secret to prevent unauthorized signing of messages.

Additionally, a trusted third-party certificate authority (CA) is used to validate the authenticity of the public key. The certificate includes information about the owner of the public key, such as their name and organization, and is signed by the CA to ensure its authenticity. However, a trusted third-party certificate is not necessary to verify the digital signature created using an RSA algorithm.