Encryption on Android is not fundamentally different than on any other Java SE platform. And as all the answers below are insecure, for either you have to understand cryptography before you start implementing or borrowing cryptography examples. Now, call encryptMessage() or decryptMessage() for desired AES Operation with required parameters

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Cellcrypt - Secure, encrypted phone calls and conference calls

Get the latest Android Beta with Call Encryption, Updated Get the new Android app Beta and try its new cool features in the hot summer season: heavily re-designed UI, secure calls via encrypted tunnel and call reconnect feature. Lock’n’Load The just-released beta version of the re-designed Android app implements a new development approach that immediately delivers these benefits: Cryptography | Android Developers Jun 22, 2020

Administration - What Does End-to-End Encryption Do?

5 Free 256-bit Encrypted Voice Calls Apps With End-to-End