1. Ledger Nano
Smartcard-based wallet hardware, private keys are created and signed offline in a secure smartcard.Nano environment is created using the Ledger Chrome application. If there is damage, losing even the theft of all bitcoin wallets will be made again with the seed.
A PIN code can also be added to the device to protect it from physical theft or hacking.
Nano Ledger can be used on Android computers or smartphones via Mycelium.
2.Trezor
Trezor hardware is different from nano ledger, in trezor is using a computer that is very small compared to smartcard. Private key is generated offline. Trezor is also the same which produces 24 words during setup, and has its own built in screen where the word seed is displayed and copied during backup.
Because trezor is an offline device, so that security is better, because the word seed is not displayed on an online computer. As well as extra passwords can be added in addition to 24 words. It provides extra security, because anyone who finds the seeds 24 words, others are free to access the funds.
3. Opendime
Opendime is a small USB stick that is useful for storing and transactions such as virtual account accounts. Connect to USB to check balance, you can shop online. The principle works only to read.
Can be used on computers / laptops, and smartphones. Files Images of QR codes and bitcoin addresses and private keys are generated on devices that no one has ever known, even users do not.