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Category:   Application (Security)  >   Libgcrypt Vendors:   Gnupg.org
(Ubuntu Issues Fix) Libgcrypt ECDSA Signature Calculation Timing Flaw Lets Local Users Obtain Private DSA Keys on the Target System
SecurityTracker Alert ID:  1041152
SecurityTracker URL:  http://securitytracker.com/id/1041152
CVE Reference:   CVE-2018-0495   (Links to External Site)
Date:  Jun 20 2018
Impact:   Disclosure of authentication information
Fix Available:  Yes  Vendor Confirmed:  Yes  Exploit Included:  Yes  
Version(s): prior to 1.8.3
Description:   A vulnerability was reported in Libgcrypt. A local user can obtain private keys in certain cases.

The code that performs modular addition in calculating ECDSA signatures does not run in constant time. A local user that can conduct memory-cache side-channel attacks against ECDSA signatures can recover the DSA private key.

This vulnerability is known as "The Return of the Hidden Number Problem" (ROHNP).

Other cryptographic libraries are affected.

[Editor's note: GnuPG uses Libgcrypt but does not use the affected ECDSA signatures in the default configuration.]

The original advisory is available at:

https://www.nccgroup.trust/us/our-research/technical-advisory-return-of-the-hidden-number-problem/

Keegan Ryan of NCC Group reported this vulnerability.

Impact:   A local user can obtain DSA private keys on the target system.
Solution:   Ubuntu has issued a fix.

The Ubuntu advisory is available at:

https://usn.ubuntu.com/usn/usn-3689-1

Vendor URL:  usn.ubuntu.com/usn/usn-3689-1 (Links to External Site)
Cause:   State error
Underlying OS:  Linux (Ubuntu)
Underlying OS Comments:  14.04 LTS, 16.04 LTS, 17.10, 18.04 LTS

Message History:   This archive entry is a follow-up to the message listed below.
Jun 20 2018 Libgcrypt ECDSA Signature Calculation Timing Flaw Lets Local Users Obtain Private DSA Keys on the Target System



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