Facebook Messenger has recently enabled security feature for messages between persons. To activate this function, click on your friend's name and select Secret Conversation, the whole conversation will be turned into confidential, which means only two of you could decrypt to read.
In fact, the process of encryption and decryption are performed automatically, so you do not have to do anything but select Secret Conversation feature. Those secured messages are black. In addition, while sending messages in secret conversation, you can choose to encrypt single message. For example, it is optional that the message would automatically disappear once your friend has seen it (just like Snapchat)
Click Secret Conversation to encrypt, then click the time button to determine the duration before messages are deleted
Facebook also provide device key so you two can compare with each other.
In fact, the process of encryption and decryption are performed automatically, so you do not have to do anything but select Secret Conversation feature. Those secured messages are black. In addition, while sending messages in secret conversation, you can choose to encrypt single message. For example, it is optional that the message would automatically disappear once your friend has seen it (just like Snapchat)
Click Secret Conversation to encrypt, then click the time button to determine the duration before messages are deleted
Facebook also provide device key so you two can compare with each other.