How to store Multiple Credit card and Debit card details in the phone ?

good ques. ..

Some app storing locally in encrypted format with master password?

Something like this? https://play.google.com/store/apps/details?id=c...

Use Bitwarden. No need to do any more research. I did last year and settled with Bitwarden.  

transpose(xchange) last 3 digits with cvv and store in mobile or email - even if someone gets access no harm

similar things - xchange last 2 digits, transpose 3rd quartet with fourth ...

Best Way Is Memorisation , Write ✍️ Each Card On Paper 1000 Times (Like Old Days School Punishment ).

I kept all card together and take a photo .

one side photo sent to WhatsApp and another photo keep in mail 

Take photographs of card along with CVV. Use 7zip to compress them into a zip file and password protect the zip with a long enough password. Now you can keep the zip in your phone and view cards by using the zip password.

Don't save all card information in one place, use password vault for card number and notes for expiry and cvv.

Create an excel file and store all data.

Use your own encryption algorithm like interchanging some digits to another.. (write 1 in place of 8 and 8 in place of 1, and do with others as well) you can use alphabet in place of numbers as well.(that you memorise only, don't write them anywhere)

You might end up having some random words written in your excel that no one can guess is a card.

Don't store all data in same file..

Like you can store first eight in one and other eight in another..

And expiry and cvv in other file.

Don't use credit card and banks word. That can trigger bots and virus to attack on that file.

I don't believe in third party apps because the biggest to biggest company got hacked and compromised data.. and hacker found benefits in cracking them. But no one wants to give time to crack your own algorithm just for few cards.

If you have less than 10, it's easy to memorize but if they are dozens, it's not possible to memorize them.

Here is an example of what practice I follow for last 10 years.

Having an Excel file with a huge password (30+ chars, complex, no dic word) to store the card number (first 12 digit as it is, last 4 digit converted with my own algorithm), expiry (as it is) CVV (converted with my own algorithm).

Not storing the file anywhere online. Just keeping a backup copy on an external storage at home.

Physical cards are kept at home with international and contact less disabled.

Hope this helps.

Opening drawer and taking out card would take equivalent time as to opening any app where you have stored the card details.

However, keeping cards in the drawer is more safe.

Use Bitwarden.com or Bitwarden app

I use it to store about 40 cards (debit + credit of all my family members)

Learn hindi numbers .. write all details in hindi digits and send it to self in Whatsap or even better at Signal