CWE-1300: Improper Protection of Physical Side Channels

Description

The device does not contain sufficient protection mechanisms to prevent physical side channels from exposing sensitive information due to patterns in physically observable phenomena such as variations in power consumption, electromagnetic emissions (EME), or acoustic emissions.

An adversary could monitor and measure physical phenomena to detect patterns and make inferences, even if it is not possible to extract the information in the digital domain. Physical side channels have been well-studied for decades in the context of breaking implementations of cryptographic algorithms or other attacks against security features. These side channels may be easily observed by an adversary with physical access to the device, or using a tool that is in close proximity. If the adversary can monitor hardware operation and correlate its data processing with power, EME, and acoustic measurements, the adversary might be able to recover of secret keys and data.

Potential Impact

Demonstrative Examples

As each character of
		    the PIN number is entered, a correct character
		    exhibits one current pulse shape while an
		    incorrect character exhibits a different current
		    pulse shape.

Rather than comparing
		    each character to the correct PIN value as it is
		    entered, the device could accumulate the PIN in a
		    register, and do the comparison all at once at the
		    end. Alternatively, the components for the
		    comparison could be modified so that the current
		    pulse shape is the same regardless of the
		    correctness of the entered
		    character.

The local method of extracting the secret key consists of plugging the key into a USB port and using electromagnetic (EM) sniffing tools and computers.

Several solutions could have been considered by the manufacturer. For example, the manufacturer could shield the circuitry in the key or add randomized delays, indirect calculations with random values involved, or randomly ordered calculations to make extraction much more difficult. The manufacturer could use a combination of these techniques.

...
				module mod_exp
					
					...
					`UPDATE: begin
						
						if (exponent_reg != 'd0) begin
							
							if (exponent_reg[0])
								
								result_reg <= result_next;
								
							base_reg <= base_next;
							exponent_reg <= exponent_next;
							state <= `UPDATE;
							
						
					...
					
				endmodule

...
				module mod_exp
					
					...
					`UPDATE: begin
						
						if (exponent_reg != 'd0) begin
							
							if (exponent_reg[0]) begin
								
								result_reg <= result_next;
								
							end else begin
								
								mask_reg <= result_next;
								
							end
							base_reg <= base_next;
							exponent_reg <= exponent_next;
							state <= `UPDATE;
							
						
					...
					
				endmodule

Mitigations & Prevention

Detection Methods

• Manual Analysis Moderate — Perform a set of leakage detection tests such as the procedure outlined in the Test Vector Leakage Assessment (TVLA) test requirements for AES [REF-1230]. TVLA is the basis for the ISO standard 17825 [REF-1229]. A separate methodology is provided by [REF-1228]. Note that sole reliance on this metho
• Manual Analysis Moderate — Post-silicon, perform full side-channel attacks (penetration testing) covering as many known leakage models as possible against test code.
• Manual Analysis Moderate — Pre-silicon - while the aforementioned TVLA methods can be performed post-silicon, models of device power consumption or other physical emanations can be built from information present at various stages of the hardware design process before fabrication. TVLA or known side-channel attacks can be appl

Real-World CVE Examples

Related Weaknesses