Hedera will be updating the Hedera Wallet for iOS / Android to v1.2 on September 9th, 2019.
This new version of the Hedera Wallet (v1.2) includes an update to the encryption standard (BIP39) used for key generation (public / private key pair and backup phrase). This updated encryption standard is used industry-wide.
After updating a Hedera Wallet that has an account ID to v1.2, you'll be asked to either ‘Accept’ or ‘Skip’ updating your public / private key pair and backup phrase. Accepting is optional, but highly recommended, especially if you plan to migrate your Hedera account to a hardware wallet or custodial service (rather than opening a new one).
If you ‘Accept’ the update, you MUST securely document your new backup phrase. It is your responsibility to ensure that your backup phrase and public / private key pairs are safely and securely documented. Hedera is unable to offer any assistance for those who have lost their public / private key pairs or backup phrase.