ECC SMS (com.woodkick.eccsms) on Google Play
To make it work in 4.4+ install following app: https://play.google.com/store/apps/details?id=droidmate.appopsinstallerThen give ECC SMS "writing sms" permissions.Made for encryption lovers! with Elliptic Curve Cryptography. - totally over sms- public-key infrastructure (PKI)- Elliptic Curve Integrated Encryption Scheme (ECIES)- equals >15360bit RSA Encryption!- protects efficiently until year 2120This means that after 2120 there may be enought computational power on earth to find the private key for decrypting the messages in a useful time. Key sharing works like in PGP SMS.Because of the strong ecryption, it needs at least 2 sms for a single conversation.Anti-Prism SMS.Attention: Currently some cyanogenmod nightlies have an error while sending multipart sms messages.