Enhance_validation_of_keychain_keychain_access_transaction_#882

[apoorv-2204]

Description

We want to avoid ddos of keychain tx and keychain access due to being free.

image by @Neylix

Fixes

• Enhance validation of keychain & keychain access transaction #882

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[samuelmanzanera]

Otherwise good PR ;)