FAQ

Before Use

Do I need a password to encrypt or decrypt files?

No, a password is not required. Instead, 4Login authentication is required.

Do I need to register for 4Login?

4Login authentication is required in the following situations:
・When decrypting files (except when using Cryptan Easy Decryption)
・When logging in to Cryptan Web
・When using Cryptan Desktop for the first time
・When using Cryptan Desktop again after an extended period of inactivity
URL:https://cryptan.jp/help/cryptan-introduce_2/

What do I need to install to use Cryptan Desktop?

If you want to encrypt or decrypt files locally on your PC, you need to download and install Cryptan Desktop.
URL:https://cryptan.jp/download/
You also need to register for a 4Login account.
URL:https://cryptan.jp/help/cryptan-introduce_2/

Can I use Cryptan without a smartphone?

4Login authentication is required in the following situations:

• When decrypting files (except when using Cryptan Easy Decryption)
• When logging in to Cryptan Web
• When using Cryptan Desktop for the first time
• When re-registering your email address in Cryptan Desktop
• When authentication is required while using Cryptan Desktop
• When using Cryptan Desktop again after an extended period of inactivity

Is Cryptan available only for Windows? Can I also use it on a Mac?

Cryptan Desktop is available only for Windows.
Cryptan Web is available on both Windows and macOS.

Can I use Cryptan for free?

RSA (conventional) encryption is available free of charge on Cryptan Web and Cryptan Desktop. However, some features require payment. Post-Quantum Cryptography (PQC) is available as a paid feature.

Can I use my Cryptan PQC perpetual license on another PC?

You can use your Cryptan PQC Perpetual License on any PC where a version of Cryptan Desktop covered by the license is installed.
However, you must be signed in with the 4Login account (registered email address) linked to your Cryptan PQC Perpetual License. The license cannot be used with a 4Login account associated with a different email address.
Please note that registered email addresses and groups are not transferred to another PC.
To transfer groups and other related information, please use Cryptan Web.
URL:https://cryptan.jp/help/group/

Can I use Cryptan for business purposes?

Cryptan can be used by companies, organizations, and local governments to protect files and help prevent data leakage.
If a company, organization, or local government is considering purchasing multiple licenses, please feel free to contact us using the contact information below.
URL:https://cryptan.jp/contacts/

Can I use Cryptan offline?

An Internet connection is required to use Cryptan. Offline use is not supported.

Are encrypted files stored on the server?

Your encrypted files and folders are not stored on servers.

Does Cryptan keep logs?

Cryptan retains logs related to service usage. However, these logs are not disclosed publicly and are not provided in response to user inquiries.
You can view your encryption and decryption history in Settings → Encryption History and Decryption History in Cryptan Web.

Can I use Cryptan outside Japan?

Cryptan Desktop can be used outside Japan. However, we do not guarantee that its use complies with the laws and regulations of the country or region where it is used. Users are responsible for complying with Japan’s Foreign Exchange and Foreign Trade Act, other applicable export control laws and regulations, and the laws and regulations of the country or region where they use Cryptan Desktop.
For details, please refer to Article 7 of the Cryptan Desktop Terms of Service.
URL:https://cryptan.jp/en/userpolicy/

Cryptan Web can also be used outside Japan. However, we do not guarantee that its use complies with the laws and regulations of the country or region where it is used. When using Cryptan Web outside Japan, users are solely responsible for complying with applicable local laws and regulations, and Passlogy shall not be liable for such use.
For details, please refer to the Cryptan Web Terms of Service.
URL:https://cryptan.jp/userpolicyweb/

Do recipients of encrypted files need to purchase Cryptan?

If you only need to decrypt encrypted files, you do not need to purchase a Cryptan PQC Perpetual License.
To decrypt PQC-encrypted files (.pqc), you must register for a free 4Login account for authentication.
To decrypt RSA-encrypted files (.p4c), a 4Login account is not required. If you do not use 4Login, please use Cryptan Easy Decryption.

Do recipients need to register for 4Login?

PQC-encrypted files (.pqc)
Recipients must register for a free 4Login account.
When decrypting the file, recipients are authenticated through 4Login. The email address specified as the recipient during encryption must match the email address registered with the recipient’s 4Login account.
If the email addresses do not match, the file cannot be decrypted.

RSA-encrypted files (.p4c)
Registration for 4Login is not required.
If the recipient has a 4Login account, they can authenticate with 4Login to decrypt the file.
Recipients who do not have a 4Login account can still decrypt the file using Cryptan Easy Decryption, provided they use the email address that was specified as the recipient when the file was encrypted.

Is an Internet connection required?

An Internet connection is required.

Is there a validity period for decrypting encrypted files?

You can set a decryption validity period when encrypting a file.

• Free version: The decryption validity period is 7 days.
• Paid version: You can choose a decryption validity period of 7, 15, 30, 60, or 90 days.
• Files encrypted for your own use: The decryption validity period is unlimited.

Once the decryption validity period has expired, the recipient can no longer decrypt the encrypted file.

How to Use Cryptan

How can I share encrypted files by email, chat, or cloud storage?

Cryptan Desktop

• Open Cryptan Desktop and click Encrypt.
• Enter your email address and the recipient’s email address, then click Next.
  • For PQC encryption, the recipient must be a 4Login user. Be sure to enter the email address that the recipient has registered with 4Login.
  • For RSA encryption, the recipient does not need to be a 4Login user.
• Drag and drop the file(s) you want to encrypt.
• Copy the encrypted file from your PC folder, then attach, paste, or upload it to the desired location, such as an email, chat application, or cloud storage service.

Cryptan Web

• Log in to Cryptan Web and click Encrypt.
• Enter your email address and the recipient’s email address, then click Next.
  • For PQC encryption, the recipient must be a 4Login user. Be sure to enter the email address that the recipient has registered with 4Login.
  • For RSA encryption, the recipient does not need to be a 4Login user.
• Drag and drop the file(s) you want to encrypt.
• Copy the encrypted file from your PC’s Downloads folder, then attach, paste, or upload it to the desired location, such as an email, chat application, or cloud storage service.

Why can’t I encrypt files?

Please check the following:

• Make sure your device is connected to the Internet.
• Make sure you are signed in to 4Login.
• Make sure your license has been activated (Cryptan Desktop only).
• Make sure you are using the latest version of Cryptan.

Where can I find my encrypted file or folder?

Cryptan Desktop
Encrypted files are saved in the folder specified under Operation Settings → Encryption File Save Location.
If no save location has been specified, the encrypted file is saved in the same location as the original file.

Cryptan Web
Encrypted files are saved in the Downloads folder on the PC used for encryption.

Where can I find my decrypted file or folder?

Cryptan Desktop
Decrypted files are saved in the folder specified under Operation Settings → Decryption File Save Location.
If no save location has been specified, the decrypted file is saved in the same location as the original file.

Cryptan Web
Decrypted files are saved in the Downloads folder on the PC used for decryption.

How can I send an encrypted file to multiple recipients?

When encrypting a file, you can specify multiple recipient email addresses.
You can also create a recipient group in advance. By specifying the group during encryption, all email addresses registered in that group will be able to decrypt the encrypted file.
After encrypting the file, send the encrypted file to the recipients whose email addresses were specified during encryption.

What should I do if I entered the wrong recipient email address?

PQC-encrypted files (.pqc)
Recipients must be 4Login users (free registration is available). In addition, the email address registered with the recipient’s 4Login account must match the email address specified during encryption.
Therefore, if you enter the recipient’s email address incorrectly, the recipient will generally not be able to decrypt the file.
If the recipient has not yet decrypted the file, you can disable decryption from Cryptan Web.

• Log in to Cryptan Web.
• Go to Settings → Encryption History.
• Select the encrypted file and click Change to disable decryption.

Note: If the recipient has already decrypted the file, decryption can no longer be disabled.

RSA-encrypted files (.p4c)
Recipients can decrypt the file using Cryptan Easy Decryption, provided they use the email address specified during encryption.
Therefore, if you enter the wrong email address, the person who has access to that email address may be able to decrypt the file.
If the recipient has not yet decrypted the file, you can disable decryption from Cryptan Web.

1. Log in to Cryptan Web.
2. Go to Settings → Encryption History.
3. Select the encrypted file and click Change to disable decryption.

Note: If the recipient has already decrypted the file, decryption can no longer be disabled.

When encrypting a file, you can also set the recipient’s decryption validity period to 7, 15, 30, 60, or 90 days.

Can I encrypt an entire folder?

Cryptan Desktop supports folder encryption.
Note: Depending on the size of the folder and your system environment, the encryption process may take some time.

Is there a file size limit for encryption?

Cryptan Web
You can encrypt one file per operation, with a maximum file size of 30 MB.

Cryptan Desktop
You can encrypt multiple files with no file size limit.
Note: Depending on the file size and your system environment, the encryption process may take some time.

Why can’t I decrypt (open) an encrypted file?

Please check the following:

• Make sure you are using the correct decryption method.
  • .pqc files Can be decrypted using Cryptan Web or Cryptan Desktop.
  • .p4c files Can be decrypted using Cryptan Web, Cryptan Desktop, or Cryptan Easy Decryption.
• Make sure you are using the correct recipient email address.
  • When using Cryptan Easy Decryption, use the email address that was specified during encryption.
  • When using Cryptan Web or Cryptan Desktop, the email address registered with your 4Login account must match the recipient email address specified during encryption.
• Make sure the decryption validity period has not expired.
  • Once the decryption validity period set by the sender has expired, the file can no longer be decrypted.
• Make sure the sender has not disabled decryption.
  • If the sender has disabled decryption, the file can no longer be decrypted.
• Make sure the file is not corrupted.
  • If the file was corrupted during email transmission or while being saved, please ask the sender to resend the encrypt

What happens if I accidentally send an encrypted file to the wrong recipient?

If the recipient has not yet decrypted the encrypted file, you can disable decryption from the Encryption History page in Cryptan Web, even after sending the encrypted file.
Once decryption has been disabled, the recipient will no longer be able to decrypt the encrypted file, even if they have already received it.
To disable decryption:

• Log in to Cryptan Web.
• Go to Settings → Encryption History.
• Select the encrypted file and click Change to disable decryption.

Note: If the recipient has already decrypted the file, decryption can no longer be disabled.

Can the recipient still decrypt the file if the email is forwarded?

Even if an email containing an encrypted file is forwarded to a third party, only the intended recipient can decrypt the file.
・PQC-encrypted files (.pqc): The recipient must authenticate with the 4Login account registered with the email address specified during encryption. Any other email address cannot be used to decrypt the file.
・RSA-encrypted files (.p4c): Authentication using the email address specified during encryption is also required. Any other email address cannot be used to decrypt the file.
Therefore, even if an email containing an encrypted file is forwarded to a third party, no one other than the intended recipient can decrypt the file.

Do I need to send a password?

You do not need to send a password separately.
Cryptan does not use passwords for decryption. Instead, it uses a system that authenticates recipients based on their email address.
・PQC-encrypted files (.pqc): Decryption requires authentication with a 4Login account registered using the email address specified as the recipient during encryption.
・RSA-encrypted files (.p4c): Decryption is performed by authenticating with the email address specified as the recipient during encryption.
Therefore, unlike conventional password-protected file sharing, there is no need to send a password separately after sending the encrypted file. This also helps reduce the risk of forgetting to send the password or sending both the encrypted file and the password through the same communication channel.

Technical Information

What is the difference between Cryptan Web and Cryptan Desktop?

For a detailed comparison of the features of Cryptan Web and Cryptan Desktop, please refer to the feature comparison table below.
URL:https://cryptan.jp/en/price/#functions

What is Cryptan Easy Decryption?

Cryptan Easy Decryption is a service that allows users who have not registered for a 4Login account to decrypt RSA-encrypted files (.p4c).
Please note that Cryptan Easy Decryption does not support the decryption of PQC-encrypted files (.pqc).

What is Post-Quantum Cryptography (PQC)?

Post-Quantum Cryptography (PQC) is a new generation of cryptographic technology designed to protect against the risk of cryptographic attacks by future quantum computers.
Cryptan uses ML-KEM, a post-quantum cryptographic algorithm standardized by the National Institute of Standards and Technology (NIST), to provide file encryption that is designed to protect files against attacks from both current computers and future quantum computers.

What is RSA?

RSA is a conventional cryptographic algorithm based on the difficulty of factoring large integers.
It is widely used today.

What is ML-KEM?

ML-KEM (Module-Lattice-Based Key-Encapsulation Mechanism) is a post-quantum cryptographic (PQC) key encapsulation algorithm standardized by the National Institute of Standards and Technology (NIST).
It is based on lattice-based cryptography and is designed to resist attacks from future quantum computers.
By adopting ML-KEM, Cryptan provides secure file encryption designed to protect data with future security in mind.

Why is Post-Quantum Cryptography (PQC) necessary?

Widely used public-key cryptographic algorithms, such as RSA and ECC, may become vulnerable once sufficiently powerful quantum computers become practical.
Many types of sensitive data need to remain secure for many years. As a result, there is a concern that data encrypted today could be intercepted, stored, and decrypted in the future using quantum computers. This threat is known as Harvest Now, Decrypt Later (HNDL).
Post-Quantum Cryptography (PQC) is designed to address this future risk and help ensure the long-term security of encrypted data.

What do the file extensions “.pqc”, “.p4c”, “.pqcx”, and “.p4cx” mean?

The file extension is automatically assigned based on the encryption algorithm and key management method used during encryption.

• .pqc: A file encrypted using Post-Quantum Cryptography (PQC).
• .p4c: A file encrypted using the RSA algorithm.

The difference between .pqc/.p4c and .pqcx/.p4cx is who can decrypt the file.

• .pqc / .p4c: The file can be decrypted by the recipients specified during encryption and by the sender.
• .pqcx / .p4cx: The file can only be decrypted by the sender.

Licensing and Purchase

What is the Cryptan PQC Perpetual License (3-Year Usage Guarantee)?

The 3-Year Usage Guarantee ensures that you can use Cryptan PQC for three years from the date of purchase in the operating environment specified by Passlogy.
After purchase, you may continue using Cryptan PQC indefinitely. However, this license does not include the right to use any future versions, successor versions, or higher editions of the product.
If Cryptan PQC becomes unusable in the operating environment specified by Passlogy during the three-year guarantee period, Passlogy will provide appropriate support, such as investigating the issue, providing a corrected version, reissuing the license, or offering a workaround, in accordance with its prescribed procedures.

What can I use after purchasing the Cryptan PQC Perpetual License (3-Year Usage Guarantee)?

After purchasing the Cryptan PQC Perpetual License (3-Year Usage Guarantee), you will have access to all Cryptan features.
For details, please refer to the following page.
URL:https://cryptan.jp/en/price/#functions

Can I change the email address associated with my Cryptan PQC Perpetual License (3-Year Usage Guarantee)?

Once a Cryptan PQC Perpetual License has been linked to a 4Login account (email address), it cannot be transferred or changed to another 4Login account (email address).