Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both encryption of plaintext and decryption of ciphertext. The keys may be identical or there may be a simple transformation to go between the two keys. The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information link. This requirement that both parties have access to the secret key is one of the main drawbacks of symmetric key encryption, in comparison to public-key encryption (also known as asymmetric key encryption). Learn More
Public or Asymmetric Key Encryption
Public key cryptography, or asymmetric cryptography, is any cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys which are known only to the owner. This accomplishes two functions: authentication, which is when the public key is used to verify that a holder of the paired private key sent the message, and encryption, whereby only the holder of the paired private key can decrypt the message encrypted with the public key. Learn More
SendSafely is an add in for either Google’s Gmail or Microsoft’s Outlook. The Gmail version, just like Gmail, is free. The Outlook version, just like Outlook, is not. It uses a synchronous algorithm (AES-256), however the receiver decrypts the email by receiving a code in an SMS message on their cell phone or in an email so the receiver does not need to have a private key nor the sender need to have the receiver’s public key. This approach combines the best of the synchronous approach but without the necessity having any keys.
The sender first invokes the SendSafely app within either gmail or Outlook, adds the recipients email address, message and attachments (step 1). SendSafely generates the “Server Secret” and provides it to the sender’s machine (Step 2). The “ClientSecret” is generated on the sender’s machine (unknown to SendSafely) and is merged with the “Server Secret” to form the key (Step 3). The sender’s machine encrypts the items and Uploads them to SendSafely using the key (Step 4).
The sender emails the “Client Secret” and a link to SendSafely to the recipient (Step 6). When the recipient attempts to connect via the email link, SendSafely sends an access code to either the recipient’s mobile phone or email address at their discretion.