Arm Mbed OS support forum

Signature part 2 (s) not matching

Dear friends,

I have included the mbed tls library in my project.
Details are :
Platform : Embedded C
Controller : MAX71315S (32 bit)
RAM size : 32 kb
Flash size : 256 kb

I have successfully generated the signature using following parameters:
ECDSA, secp256r1

Private key : AE 55 41 4F FE 07 9F 9F C9 56 49 53 6B D1 C2 B5 65 3D 20 08 13 72 7E 07 D5 01 A8 B5 50 C6 92 07

Input data : 0x00,0x08,0x73,0x79,0x73,0x74,0x69,0x74,0x6C,0x65,0x08,0x71,0x77,0x65,0x72,0x74,0x79,0x75,0x69,0x00,0x00,0x08,0x00,0x06,0x5F,0x1F,0x04,0x00,0x00,0x18,0x1D,0x04,0x00,0x00,0x07

Hash of the data (SHA256) : 0A4E42FE33E43036B0776664607A7F93AECE56049568B4606142FAF68EEED9C3

Random number: F2913B09236C260D89496C2000942D3BE981F23E9A7B1E3BAA5F704E702AF89D

Signature:
R :
66120A46685A3069500149358A1841F74B02B2B95EEC12C9DE139278F2C642E8
S :
B271D01529E51CEB69A6CF0BFED88EB97A636B9B57ABBE47F651DBBAFE05F72

But when i verify the signature by using the tool SCV cryptomanager i am getting following for same inputs:
R :
66120A46685A3069500149358A1841F74B02B2B95EEC12C9DE139278F2C642E8
S :
B9B6F263A11F767F6A4FB7C942A52D64B334B6848D3EB969C9B238CFECD7B9EC

Conclusion :
R part of signature matches.
S part of signature is different.

Query :
Why S part of signature is different.

Thanks