File Encryption Software "ED" where encrypted data may be easier to decipher when files of small size are encrypted


File encyption software "ED" contains an issue when files of small size are encyrpted, they may become easier to decipher in comparison to when files of a larger size are encrypted.

When encrypting small files that are smaller than the block size (128 bits), file encryption software "ED" encrypts such files with "a stream cipher combining ECB mode of the selected encryption algorithm on key generation". This results in deciphering the resulting encrypted data to become relatively easy. For more details on this specification, pelase refer to the documentation (http://type74.org/edman5-1.php) provided by the developer.

Yutaka Sawada reported this vulnerability to IPA.
JPCERT/CC coordinated with the developer under Information Security Early Warning Partnership.
CVSS Severity (What is CVSS?)

CVSS V2 Severity:
Base Metrics 2.6 (Low) [IPA Score]
  • Access Vector: Network
  • Access Complexity: High
  • Authentication: None
  • Confidentiality Impact: Partial
  • Integrity Impact: None
  • Availability Impact: None
This analysis assumes that a file less than 16 bytes has been encrypted and an attacker is attempting to decipher this encrypted data.
Affected Products

  • File encryption software "ED" prior to Ver4.0


When a file that is less than 16 bytes in size is encrypted, there is a possibility that it can be deciphered through differential cryptanalysis.

[Update the software]
Update the software to Ver4.0 or later according to the information provided by the developer.

[Apply a Workdaround]
If an update to Ver4.0 or later cannot be applied, the following workaround will mitigate effects of this issue.
- Do not encrypt files less than 16 bytes in size
Vendor Information

CWE (What is CWE?)

  1. No Mapping(CWE-DesignError) [IPA Evaluation]
CVE (What is CVE?)

  1. CVE-2015-2987

  1. JVN : JVN#91474878
  2. National Vulnerability Database (NVD) : CVE-2015-2987
Revision History

  • [2015/08/27]
      Web page was published
      References : Content was added
      Vendor Information : Content was added