In Bouncy Castle for Java before 1.86, NTRU reduced secret values with the % operator in three helpers whose reference implementations are deliberately division-free, so each reduction was carried out by an integer division whose latency depends on the secret operand. Polynomial.modQ divided by a variable divisor, which a compiler cannot strength-reduce to a multiply the way it can a constant one, so it emitted a division on every call including on the decapsulation path where the dividend derives from the private key; Polynomial.mod3 and NTRUSampling.mod3 divided the secret key polynomials f and g during key generation, the message polynomials r and m during encapsulation, and coefficients recovered during decapsulation. An attacker able to measure that timing can recover information about the NTRU private key. modQ now masks, which is exact because q is always a power of two, and mod3 uses the reference implementation's division-free fold and select; the results are unchanged.
CVSS
No CVSS.
References
Configurations
No configuration.
History
02 Oct 2026, 08:17
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-10-02 08:17
Updated : 2026-10-02 18:17
NVD link : CVE-2026-18036
Mitre link : CVE-2026-18036
CVE.ORG link : CVE-2026-18036
JSON object : View
Products Affected
No product.
CWE
CWE-208
Observable Timing Discrepancy