JVN#91474878
File Encryption Software "ED" where encrypted data may be easier to decipher when files of small size are encrypted
Overview
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.
Products Affected
- File encryption software "ED" prior to Ver4.0
Description
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 provided by the developer.
Impact
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.
Solution
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 Status
| Vendor | Link |
| Type74.org | ED Manual - 5-1 - About Encryption Algorithms |
| File Encryption Software "ED" |
References
JPCERT/CC Addendum
Vulnerability Analysis by JPCERT/CC
Analyzed on 2015.08.27 (CVSS Base Metrics)
| Measures | Severity | Description | ||
|---|---|---|---|---|
| Access Vector(AV) | Local (L) | Adjacent Network (A) | Network (N) | A vulnerability exploitable with network access means the vulnerable software is bound to the network stack and the attacker does not require local network access or local access. Such a vulnerability is often termed "remotely exploitable". |
| Access Complexity(AC) | High (H) | Medium (M) | Low (L) | Specialized access conditions exist. |
| Authentication(Au) | Multiple (M) | Single (S) | None (N) | Authentication is not required to exploit the vulnerability. |
| Confidentiality Impact(C) | None (N) | Partial (P) | Complete (C) | There is considerable informational disclosure. Access to some system files is possible, but the attacker does not have control over what is obtained, or the scope of the loss is constrained. |
| Integrity Impact(I) | None (N) | Partial (P) | Complete (C) | There is no impact to the integrity of the system. |
| Availability Impact(A) | None (N) | Partial (P) | Complete (C) | There is no impact to the availability of the system. |
Base Score:2.6
Comment
This analysis assumes that a file less than 16 bytes has been encrypted and an attacker is attempting to decipher this encrypted data.
Credit
Yutaka Sawada reported this vulnerability to IPA.
JPCERT/CC coordinated with the developer under Information Security Early Warning Partnership.
Other Information
| JPCERT Alert |
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| JPCERT Reports |
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| CERT Advisory |
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| CPNI Advisory |
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| TRnotes |
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| CVE |
CVE-2015-2987 |
| JVN iPedia |
JVNDB-2015-000119 |