The basic protocol for the **Asymmetric Cryptography** works as the following:

- Either the sender or the receiver,
**Bob**for example, will generate two keys (**public-key**and**private-key**). **Bob**will distribute his (**public-key**) publicly to everyone.- The other parties,
**Alice**for example, will use Bobâ€™s (**public-key**) to send an encrypted message back to Bob. **Bob**will receive the (**encrypted**) message from**Alice**(*unreadable message up till now*).**Bob**will use his (**private-key**) to decrypt the received message (*become readable now*).

Note: if **Oscar** interrupt the communication and gain the encrypted message, it will be very difficult for him to decrypt it, since Bob only has the (**private-key**).

As a real-life example, everyone has an email address nowadays, where every email is linked with a secret password. Think of it this way, you give your email address to other people to send you emails/messages (**public-key**), while you are the only person who can read this emails/messages by accessing to your email address with your private password (**private-key**).

The main services that Asymmetric Cryptography provides:

**Key Distribution:**For example, Diffie-Hellman Key Exchange & RSA (without a pre-shared secret key).**Non-repudiation and Digital Signatures:**For example, RSA, DSA or ECDSA. (that provides message integrity).**Identification:**Using challenge-response protocols with digital signatures.**Encryption:**For example, RSA/Elgamal.

However, the main **disadvantage** that **Asymmetric Algorithms** is about 1000 times slower than **Symmetric Algorithms** (__Computationally very intensive__).

In conclusion, it looks as though **Asymmetric Cryptography** (**public-key schemes**) can provide all functionality needed in modern security protocols such as **SSL/TLS.** However, the major drawback in practice is that **encryption** of data is extremely computationally demanding with (**public-key algorithms**). Many **Block** and **Stream** **ciphers** can encrypt 1000 times faster in software than (**public-key algorithms**). On the other hand, **Symmetric Cryptography (private-key algorithms)** are __poor at providing digital signatures__ and __key establishment/transport functionality__. Hence, most practical protocols are **hybrid protocols**, which incorporate both **Symmetric Algorithms** and **Asymmetric Algorithms**.