What are the principles of Public key Cryptosystem in Information Security?

Public key cryptography has become an essential means of providing confidentiality, especially through its need of key distribution, where users seeking private connection exchange encryption keys. It also features digital signatures which enable users to sign keys to check their identities.

The approach of public key cryptography derivative from an attempt to attack two of the most complex problems related to symmetric encryption. The first issue is that key distribution. Key distribution under symmetric encryption needed such as −

  • that two communicants already shared a key, which somehow has been shared to them.

  • the need of a key distribution center.

Public key Cryptosystem − Asymmetric algorithms depends on one key for encryption and a distinct but related key for decryption. These algorithms have the following characteristics which are as follows −

  • It is computationally infeasible to decide the decryption key given only information of the cryptographic algorithm and the encryption key.

  • There are two related keys such as one can be used for encryption, with the other used for decryption.

A public key encryption scheme has the following ingredients which are as follows −

  • Plaintext − This is the readable message or information that is informer into the algorithm as input.

  • Encryption algorithm − The encryption algorithm performs several conversion on the plaintext.

  • Public and Private keys − This is a set of keys that have been selected so that if one can be used for encryption, and the other can be used for decryption.

  • Ciphertext − This is scrambled message generated as output. It based on the plaintext and the key. For a given message, there are two specific keys will create two different ciphertexts.

  • Decryption Algorithm − This algorithm get the ciphertext and the matching key and create the original plaintext.

The keys generated in public key cryptography are too large including 512, 1024, 2048 and so on bits. These keys are not simply to learn. Thus, they are maintained in the devices including USB tokens or hardware security modules.

The major issue in public key cryptosystems is that an attacker can masquerade as a legal user. It can substitutes the public key with a fake key in the public directory. Moreover, it can intercepts the connection or alters those keys.

Public key cryptography plays an essential role in online payment services and ecommerce etc. These online services are ensure only when the authenticity of public key and signature of the user are ensure.

The asymmetric cryptosystem should manage the security services including confidentiality, authentication, integrity and non-repudiation. The public key should support the security services including non-repudiation and authentication. The security services of confidentiality and integrity considered as an element of encryption process completed by private key of the user.

Updated on: 16-Mar-2022

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