#Step1 : Create a custom object name encryptExample.

#Step2: Now create a visualforce page to encrypt and decrypt the name of the  object which we have created.

<apex:page standardController="EncrptExample__c" extensions="encrptExample" sidebar="false">
    <!-- 
        /**
        * Webkul Software.
        *
        * @category  Webkul
        * @author    Webkul
        * @copyright Copyright (c) 2010-2017 Webkul Software Private Limited (https://webkul.com)
        * @license   https://store.webkul.com/license.html
        */ 
	-->
    <apex:form >
        <apex:pageBlock >
            <apex:pageBlockSection columns="3">
                <apex:pageBlockSectionItem >
                    <apex:commandButton value="Encrypt" action="{!Save}"/>
                </apex:pageBlockSectionItem>
                <apex:pageBlockSectionItem >
                    <apex:inputField value="{!encrypt.Name}"/>
                </apex:pageBlockSectionItem>
                <apex:pageBlockSectionItem >
                    <apex:commandButton value="Decrypt" action="{!test}"/>
                </apex:pageBlockSectionItem>
            </apex:pageBlockSection>
        </apex:pageBlock>
    </apex:form> 
</apex:page>

#Step3: Create apex class name encrptExample to encrypt and decrypt the name of the object.

public class encrptExample {
    
    /**
    * Webkul Software.
    *
    * @category  Webkul
    * @author    Webkul
    * @copyright Copyright (c) 2010-2017 Webkul Software Private Limited (https://webkul.com)
    * @license   https://store.webkul.com/license.html
    */ 
    public EncrptExample__c encrypt{get;set;}
    
    Blob cryptoKey = Crypto.generateAesKey(256);
    public Id recordId{get;set;}
    public encrptExample(ApexPages.StandardController controller) {
        recordId = Apexpages.CurrentPage().getParameters().get('id');
        if(recordId !=null){
            encrypt = [SELECT id,Name From EncrptExample__c 
                       WHERE id=:recordId];
        }
        else{
            encrypt = new EncrptExample__c();
        }
    }
    
    public PageReference Save(){
        
        Blob data = Blob.valueOf(encrypt.Name);
        Blob encryptedData = Crypto.encryptWithManagedIV('AES256', cryptoKey , data );
        String b64Data = EncodingUtil.base64Encode(encryptedData);
        encrypt.name = b64Data ;
        upsert encrypt;
        return null; 
    }
    public PageReference test(){
        Blob data = EncodingUtil.base64Decode(encrypt.Name);
        Blob decryptedData = Crypto.decryptWithManagedIV('AES256', cryptoKey , data);
        String dryptData = decryptedData.toString();
        encrypt.name = dryptData;
        
        update encrypt;
        return null; 
    }
}

In above class we use a key for encryption and decryption by using Crypto.generateAesKey(256) method. Now we use Crypto.encryptWithManagedIV(encryptionMethod, key, data to encrypt(in blob)) for encryption and  Crypto.decryptWithManagedIV(encryptionMethod, key, data to decrypt(in blob)) for decryption.

#After Encryption

#After Decryption