What is the TC file format?
A .tc file is an encrypted virtual disk volume created by TrueCrypt, an open-source disk encryption application discontinued abruptly in May 2014. When mounted, a .tc container presents as a regular drive letter - any filesystem placed inside (FAT32, NTFS, exFAT, ext4) becomes fully accessible. Unmounted, the file resembles a block of random data with no identifying header, by design.
The format's defining feature is plausible deniability: .tc files carry no magic bytes or plaintext signature. A standard volume opens with a 512-byte random salt followed by an AES-XTS-encrypted volume header, with a backup header stored in the last 64 KB of the file. A hidden volume can be nested inside the outer volume's free space - without the correct passphrase, its presence cannot be confirmed.
Supported ciphers include AES-256, Serpent-256, and Twofish-256 (all in XTS mode), as well as cascaded combinations such as AES-Twofish or AES-Twofish-Serpent. Volume headers are protected by PBKDF2-HMAC-SHA-512.
TrueCrypt 7.1a (February 2012) was the last stable release before the project's unexplained shutdown. An independent audit in 2015 found no critical backdoors but noted implementation weaknesses. VeraCrypt (IDRIX) is the active successor and reads .tc volumes in compatibility mode - however, VeraCrypt 1.26 (October 2023) removed that support. Users needing to migrate legacy .tc volumes should use VeraCrypt 1.25.9 or earlier, then convert to VeraCrypt format.
The .tc extension is not mandatory; TrueCrypt volumes can use any extension or none at all.
Security & safety
RISK: MEDIUMTrueCrypt itself is abandoned and has known (medium-severity) security bugs unfixed since 2014. DO NOT use TrueCrypt for new encryption - use VeraCrypt. Existing .tc volumes are safe to open with VeraCrypt (TrueCrypt mode) for migration purposes only. WARNING: Numerous third-party sites offer TrueCrypt downloads - these are potential malware vectors since the original source is gone. Only use VeraCrypt from veracrypt.fr for any encryption work. VeraCrypt ≥ 1.26 (Oct 2023) no longer mounts TrueCrypt volumes, so migrate existing .tc files to VeraCrypt format using VeraCrypt 1.25.9 before updating.
Format details
in a nutshellPrograms that open TC files
Windows2 apps
VeraCrypt
Open-source Use VeraCrypt version ≤ 1.25.9: click 'Select File', choose the .tc file, click 'Mount', check 'TrueCrypt Mode' in the password dialog, enter the passphrase. For new volumes, use native VeraCrypt format instead.
TrueCrypt 7.1a (historical reference only)
Open-source DO NOT use - project abandoned 2014, no security updates. Use VeraCrypt instead. TrueCrypt.org is defunct. 
macOS1 app
VeraCrypt
Open-source Same as Windows - use VeraCrypt ≤ 1.25.9 for TrueCrypt mode mount. Available as a macOS installer from veracrypt.fr. 
Linux1 app
VeraCrypt
Open-source CLI: veracrypt --truecrypt --mount /path/to/volume.tc /mnt/tc (VeraCrypt ≤ 1.25.9 only). GUI version also available. Technical details
deep spec| Encryption ciphers | AES-256, Serpent-256, Twofish-256 (XTS mode); cascaded pairs and triples also supported (e.g., AES-Twofish, AES-Twofish-Serpent) |
| Key derivation | PBKDF2-HMAC-SHA-512 (default); also SHA-1, RIPEMD-160, Whirlpool; derives the volume header decryption key |
| Plausible deniability | No magic bytes or plaintext signature - volumes appear as random data; hidden volumes can be nested inside outer volume free space |
| Volume header structure | 512-byte random salt + 512-byte AES-XTS-encrypted header; backup header in the last 64 KB of the volume |
| Hidden volume support | Yes - a second encrypted filesystem nested in the outer volume's free space; indistinguishable without the inner passphrase |
| Filesystem inside | FAT32, NTFS, exFAT, or ext2/3/4 - formatted by the user inside the encrypted container |
| Header integrity | CRC-32 over decrypted header fields; HMAC-SHA-512 on the backup header |
| Volume size | User-defined at creation - from a few MB up to several TB; fixed after creation, not dynamically expandable |
| Byte order | Little-endian |
| Platform support | Windows, macOS, Linux (original TrueCrypt); same via VeraCrypt 1.25.9 or earlier for legacy .tc volume mounting |
| Last stable release | TrueCrypt 7.1a, February 2012; project discontinued May 28, 2014 |
| Successor tool | VeraCrypt (IDRIX, 2013-present); VeraCrypt 1.26+ (October 2023) dropped TrueCrypt volume mounting and conversion |
| Released | 2004 (TrueCrypt 1.0) |
| Latest version | TrueCrypt 7.1a (February 2012) - last stable release before project abandonment |
| Specification | en.wikipedia.org |
Community Q&A
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