Re: [mbed-tls] Print long MPI - mbed-tls

27 Aug 2020


      Hello,
4096 bytes is a lot larger than a typical public key. 4096 *bits* is
common for an RSA key. Are you sure you're using the correct units?
By default the library doesn't support the creation of MPI that are
larger than 1024 bytes. This is a configuration option
(MBEDTLS_MPI_MAX_SIZE), although it's uncommon to change it (a larger
value is hardly ever necessary, and a smaller value won't save memory
except in RSA which needs at least 512 bytes for 4096-bit keys). However
mbedtls_mpi_write_file itself doesn't have any size limit.
Best regards,
-- 
Gilles Peskine
Mbed TLS developer

On 27/08/2020 13:27, youssouf sokhona via mbed-tls wrote:
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> Hello everyone, I think you are fine during this crisis.
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> I am working now with mbedtls modulee, and I wanted to print a
> function « mbedtls_mpi_write_file » to print the value of an MPI. This
> function works with common values.
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> However, when I want to print an MPI which is very long (about 4096
> bytes, a public key), it doesn’t work. Someone knows how to solve this
> problem ?
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> Thanks a lot
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> Best regards, YS
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