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Slide1. Hello dear participants!

The theme of my investigation is systems of secure communication support using the digital signature

Slide 2. Cryptography seems to be closely linked to modern electronic communication. However,cryptography is rather old, with early examples dating back to about the year 2000 B.C., when “secret” hieroglyphics were used in ancient Egypt.

Since Egyptian days cryptography has been used in one form or the other in many,

cultures that developed written language. For instance, there are documented cases of secret writing in ancient Greece, namely the Spartan scytale

It was used by generals in the ancient city-state Sparta. The way it works is as follows. Two generals would have two identical cylinders. One would encode a message by wrapping a piece of paper around the cylinder and writing a message. He would then give it, unwrapped, to the other general, who would use his identical cylinder to decode it.

Slide 3. All cryptography from ancient times until 1976 was exclusively based on symmetric methods. Symmetric ciphers are still widespread, especially for data encryption and integrity check of messages.

Symmetric Encryption is a type of encryption where the same secret key is used to encrypt and decrypt information or there is a simple transform between the two keys.

A secret key can be a number, a word, or just a string of random letters. Secret key is applied to the information to change the content in a particular way. Symmetric algorithms require that both the sender and the receiver know the secret key, so they could encrypt and decrypt the information.

The imperfection of Symmetric Encryption consists in:

Key (shared secret) is vulnerable to discovery;

Need to share a unique secret key with each party that you wish to securely communicate with. Key management becomes unmanageable.

Slide 4. Asymmetric (or Public-Key) Algorithms In 1976 an entirely different type of cipher was introduced by Whitfield Diffie and Martin Hellman. In public-key cryptography, a user possesses a secret key as in symmetric cryptography because he has a public key. Asymmetric algorithms can be used for applications such as digital signatures and key establishment, and also for classical data encryption.

The features of asymmetric encryption are:

No shared secret key;

Public key is public: it сan be freely distributed or published, key management is much easier;

Private key is known ONLY to owner: it is less vulnerable and it is easier to keep secret.

To uderstand asymmetric encryption better please look at this slide. For example, Ted and Carol make public and private key. When they have exchanged keys, Ted can send an encrypted message to Carol by using Carol's public key to scramble the message. Carol uses her private key to unscramble it. If Carol wants to send an encrypted message to Ted, she uses Ted's public key to encrypt her message. Asymmetric cryptography is usually slower to execute electronically than symmetric cryptography.

Slide 5. A digital signature works by creating a message digest which is generated by running the entire message through a hash algorithm. This generated number is then encrypted with the Sue’s private key and added to the end of the message.

When the recipient receives the message they run the message through the same hash algorithm and generate the message digest number. Then the signature using the senders public key is decrypted and the signature is valid if the two hashes match.

The theme of my investigation is systems of secure communication support using the digital signature

Slide 2. Cryptography seems to be closely linked to modern electronic communication. However,cryptography is rather old, with early examples dating back to about the year 2000 B.C., when “secret” hieroglyphics were used in ancient Egypt.

Since Egyptian days cryptography has been used in one form or the other in many,

cultures that developed written language. For instance, there are documented cases of secret writing in ancient Greece, namely the Spartan scytale

It was used by generals in the ancient city-state Sparta. The way it works is as follows. Two generals would have two identical cylinders. One would encode a message by wrapping a piece of paper around the cylinder and writing a message. He would then give it, unwrapped, to the other general, who would use his identical cylinder to decode it.

Slide 3. All cryptography from ancient times until 1976 was exclusively based on symmetric methods. Symmetric ciphers are still widespread, especially for data encryption and integrity check of messages.

Symmetric Encryption is a type of encryption where the same secret key is used to encrypt and decrypt information or there is a simple transform between the two keys.

A secret key can be a number, a word, or just a string of random letters. Secret key is applied to the information to change the content in a particular way. Symmetric algorithms require that both the sender and the receiver know the secret key, so they could encrypt and decrypt the information.

The imperfection of Symmetric Encryption consists in:

Key (shared secret) is vulnerable to discovery;

Need to share a unique secret key with each party that you wish to securely communicate with. Key management becomes unmanageable.

Slide 4. Asymmetric (or Public-Key) Algorithms In 1976 an entirely different type of cipher was introduced by Whitfield Diffie and Martin Hellman. In public-key cryptography, a user possesses a secret key as in symmetric cryptography because he has a public key. Asymmetric algorithms can be used for applications such as digital signatures and key establishment, and also for classical data encryption.

The features of asymmetric encryption are:

No shared secret key;

Public key is public: it сan be freely distributed or published, key management is much easier;

Private key is known ONLY to owner: it is less vulnerable and it is easier to keep secret.

To uderstand asymmetric encryption better please look at this slide. For example, Ted and Carol make public and private key. When they have exchanged keys, Ted can send an encrypted message to Carol by using Carol's public key to scramble the message. Carol uses her private key to unscramble it. If Carol wants to send an encrypted message to Ted, she uses Ted's public key to encrypt her message. Asymmetric cryptography is usually slower to execute electronically than symmetric cryptography.

Slide 5. A digital signature works by creating a message digest which is generated by running the entire message through a hash algorithm. This generated number is then encrypted with the Sue’s private key and added to the end of the message.

When the recipient receives the message they run the message through the same hash algorithm and generate the message digest number. Then the signature using the senders public key is decrypted and the signature is valid if the two hashes match.

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