What is a .dclk file?

Understanding DocuLock's encrypted file format.

A .dclk file is DocuLock's encrypted file format. When you encrypt a document or folder with DocuLock, the result is saved as a binary file with the .dclk extension.

How it works

Encryption happens in your browser before upload. Your files are never sent to our servers in plaintext. Only the encrypted .dclk blob is stored or transmitted.

File structure

Each .dclk file is a binary format:

  • Magic bytes (4 bytes): DCLK — identifies the file as a DocuLock encrypted file
  • Version (1 byte): format version
  • Salt (16 bytes): random salt used for key derivation
  • IV (12 bytes): initialization vector for encryption
  • Ciphertext: the encrypted content plus the auth tag

Encryption details

DocuLock uses:

  • AES-256-GCM for encryption
  • PBKDF2-SHA-256 with 600,000 iterations to derive the key from your passphrase
  • Random salt and IV per file — so each encryption is unique even with the same passphrase

Encrypting and decrypting

To create a .dclk file, use the Encrypt tool on DocuLock.Site. After encryption, you download two files: the encrypted .dclk file and a companion .dclkey key file that contains the generated decryption key. To decrypt, upload the matching .dclk and .dclkey files in the same tool.

Important

The .dclk file and its matching .dclkey file are a pair. If either one is missing, decryption will fail. Keep both files in a safe place, and do not share your key file unless you intend to grant access to the encrypted document. See What is a .dclkey file? for details.

Back to Resources What is a .dclkey file? Encrypt tool