Encrypted file created by Cryptra, a program used for securing data sent via email; contains a file that was encrypted using one of many available One Time Pad (OTP) keys provided on a CD (or .ISO image) with the software.

CRYPTRA files are used for sending files securely as email attachments. Once received, they must be decrypted using both the Cryptra software and the OTP CD that was used to encrypt the files. Therefore, in order to successfully encrypt and decrypt a CRYPTRA file, both the sender and receiver must have the Cryptra software installed and a copy of the exact same OTP CD that was used for the encryption. Each OTP CD provided with Cryptra includes the capability to encode up to 9,600 files, each of up to 64KB in size. Larger files can be encrypted using multiple keys together. Since OTP codes should only be used once, BMB Software provides a service to give users additional OTP CDs.