Crypto 101: A HandsOn Guide to Cryptography
Are you fascinated by the world of cryptography? Do you want to learn how to secure your data and communications using encryption techniques? If yes, then you have come to the right place. In this article, we will provide you with a handson guide to cryptography, covering the basics of encryption, decryption, and key management. So, let's get started!
What is Cryptography?
Cryptography is the practice of securing information by converting it into a code that can only be deciphered by authorized parties. It involves the use of mathematical algorithms to transform plaintext (unencrypted data) into ciphertext (encrypted data) and vice versa. Cryptography is used to protect sensitive information such as passwords, credit card numbers, and other personal data.
Types of Cryptography
There are two main types of cryptography: symmetric and asymmetric.
Symmetric Cryptography
Symmetric cryptography, also known as secretkey cryptography, uses the same key for both encryption and decryption. The sender and receiver of the message must have the same key to communicate securely. Symmetric cryptography is faster and more efficient than asymmetric cryptography, but it requires a secure method of key exchange.
Asymmetric Cryptography
Asymmetric cryptography, also known as publickey cryptography, uses two different keys for encryption and decryption. The sender uses the receiver's public key to encrypt the message, and the receiver uses their private key to decrypt it. Asymmetric cryptography is slower than symmetric cryptography, but it eliminates the need for a secure method of key exchange.
Encryption and Decryption
Encryption is the process of converting plaintext into ciphertext using a cryptographic algorithm and a key. Decryption is the process of converting ciphertext back into plaintext using the same cryptographic algorithm and key.
Symmetric Encryption
Symmetric encryption uses a single key for both encryption and decryption. The most common symmetric encryption algorithms are Advanced Encryption Standard (AES), Data Encryption Standard (DES), and Triple DES (3DES).
To encrypt a message using symmetric encryption, follow these steps:
 Choose a symmetric encryption algorithm and a key.
 Convert the plaintext into binary format.
 Divide the plaintext into blocks of fixed size.
 Apply the encryption algorithm to each block using the key.
 Combine the encrypted blocks into a single ciphertext.
To decrypt a message using symmetric encryption, follow these steps:
 Choose the same symmetric encryption algorithm and key used for encryption.
 Divide the ciphertext into blocks of fixed size.
 Apply the decryption algorithm to each block using the key.
 Combine the decrypted blocks into a single plaintext.
Asymmetric Encryption
Asymmetric encryption uses two different keys for encryption and decryption. The most common asymmetric encryption algorithms are RSA and Elliptic Curve Cryptography (ECC).
To encrypt a message using asymmetric encryption, follow these steps:
 Obtain the receiver's public key.
 Convert the plaintext into binary format.
 Apply the encryption algorithm to the plaintext using the receiver's public key.
 Combine the encrypted blocks into a single ciphertext.
To decrypt a message using asymmetric encryption, follow these steps:
 Use the receiver's private key to decrypt the ciphertext.
 Apply the decryption algorithm to the ciphertext using the receiver's private key.
 Combine the decrypted blocks into a single plaintext.
Key Management
Key management is the process of generating, storing, distributing, and revoking cryptographic keys. It is essential to ensure the security and integrity of encrypted data.
Symmetric Key Management
Symmetric key management involves the following steps:
 Generate a random symmetric key.
 Store the key securely.
 Distribute the key to authorized parties using a secure method.
 Revoke the key if it is compromised or no longer needed.
Asymmetric Key Management
Asymmetric key management involves the following steps:
 Generate a publicprivate key pair.
 Store the private key securely.
 Distribute the public key to authorized parties.
 Revoke the private key if it is compromised or no longer needed.
HandsOn Lab: Encrypting and Decrypting a Message
Now that you have learned the basics of cryptography, it's time to put your knowledge into practice. In this handson lab, you will encrypt and decrypt a message using symmetric and asymmetric encryption.
Requirements
To complete this lab, you will need the following:
 A computer with an internet connection
 A text editor
 OpenSSL (for asymmetric encryption)
Symmetric Encryption

Open a text editor and create a new file.

Type a message that you want to encrypt.

Save the file as
plaintext.txt
. 
Open a terminal window and navigate to the directory where
plaintext.txt
is saved. 
Type the following command to generate a random symmetric key:
openssl rand hex 16 > key.txt
This command generates a 16byte (128bit) random key and saves it to a file named
key.txt
. 
Type the following command to encrypt the message using the symmetric key:
openssl enc aes128cbc in plaintext.txt out ciphertext.bin pass file:key.txt
This command encrypts the message using the AES128CBC algorithm and the key stored in
key.txt
. The encrypted message is saved to a file namedciphertext.bin
. 
Type the following command to decrypt the message using the symmetric key:
openssl enc d aes128cbc in ciphertext.bin out decrypted.txt pass file:key.txt
This command decrypts the message using the AES128CBC algorithm and the key stored in
key.txt
. The decrypted message is saved to a file nameddecrypted.txt
. 
Open
decrypted.txt
to verify that the message has been decrypted correctly.
Asymmetric Encryption

Open a text editor and create a new file.

Type a message that you want to encrypt.

Save the file as
plaintext.txt
. 
Open a terminal window and navigate to the directory where
plaintext.txt
is saved. 
Type the following command to generate a publicprivate key pair:
openssl genpkey algorithm RSA out private.pem openssl rsa in private.pem pubout out public.pem
This command generates an RSA key pair and saves the private key to a file named
private.pem
and the public key to a file namedpublic.pem
. 
Type the following command to encrypt the message using the public key:
openssl rsautl encrypt inkey public.pem pubin in plaintext.txt out ciphertext.bin
This command encrypts the message using the RSA algorithm and the public key stored in
public.pem
. The encrypted message is saved to a file namedciphertext.bin
. 
Type the following command to decrypt the message using the private key:
openssl rsautl decrypt inkey private.pem in ciphertext.bin out decrypted.txt
This command decrypts the message using the RSA algorithm and the private key stored in
private.pem
. The decrypted message is saved to a file nameddecrypted.txt
. 
Open
decrypted.txt
to verify that the message has been decrypted correctly.
Conclusion
Congratulations! You have completed the handson guide to cryptography. You have learned the basics of encryption, decryption, and key management, and you have practiced encrypting and decrypting a message using symmetric and asymmetric encryption. Cryptography is a fascinating field, and there is always more to learn. Keep exploring and experimenting, and you will become a cryptography expert in no time!
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