RM0453 Rev 1 715/1461
RM0453 Public key accelerator (PKA)
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Note: If error output is different from zero the content of the PKA memory should be cleared to
avoid leaking information about the private key.
Extended ECDSA support
PKA also supports Extended ECDSA signature, for which the inputs and the outputs have
the same ECDSA signature (Table 162 and Table 163, respectively), with the addition of the
coordinates of the point kG. This extra output is defined in Table 164.
Table 162. ECDSA sign - Inputs
Parameters with direction Value (Note) Storage Size
IN
MODE 0x24 PKA_CR 6 bits
Curve prime order n
length
(in bits, not null) RAM@0x400
32 bitsCurve modulus p length (in bits, 8 < value < 640) RAM@0x404
Curve coefficient a sign
0x0: positive
0x1: negative
RAM@0x408
Curve coefficient |a| (Absolute value, |a| < p) RAM@0x40C
EOS
Curve modulus value p
(Odd integer prime,
0 < p < 2
640
)
RAM@0x460
Integer k
(1)
1. This integer is usually a cryptographically secure random number, but in some cases k could be
deterministically generated.
(0 ≤ k < 2
640
) RAM@0x508
Curve base point G
coordinate x
(x < p)RAM@0x55C
Curve base point G
coordinate y
(y < p) RAM@0x5B0
Hash of message z (z < 2M) RAM@0xDE8
Private key d (positive integer) RAM@0xE3C
Curve prime order n (integer prime) RAM@0xE94
Table 163. ECDSA sign - Outputs
Parameters with direction Value (Note) Storage Size
OUT
Signature part r (0 < r < n) RAM@0x700
EOS
Signature part s (0 < s < n) RAM@0x754
ERROR Result of signature
– 0x0: no error
– 0x1: signature part r is equal to 0
– 0x2: signature part s is equal to 0
RAM@0xEE8 32 bits
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