A financial institution plans to migrate its entire data processing infrastructure to a Cloud environment to support its various banking operations. The institution processes $100$ different types of transactions daily, with an average of $50,000$ transactions per type. Each transaction involves multiple steps, including validation, authorization, logging$,$ and auditing. Customers access the banking services through various channels such as mobile apps, web portals, and ATMs.

You are tasked with designing a Cloud$-$based data security and processing system that meets the following requirements:

$$ Ensure encryption of data at rest, in transit, and during processing.

$$ Implement fine$-$grained access controls based on the role and identity of the users.

$$ Provide real$-$time monitoring and logging of all access to sensitive data.

$$ Implement a data redundancy strategy to ensure zero data loss, even during catastrophic failures.

$$ Design a data segregation strategy to isolate sensitive customer data from general transaction data.

$($a$)$ Identify the challenges, available solutions, and your choice of solution with justification.

$($b$)$ Draw a diagram of the proposed Cloud security architecture, highlighting key components such as encryption mechanisms, access control layers, data redundancy methods, and monitoring systems. $[6+6=12$ marks$]$