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Post Closed as "Duplicate" by Squeamish Ossifrage, kelalaka, Maarten Bodewes♦
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kelalaka
kelalaka
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I've been experimenting with MBEDTLS on an ARM-M4 (but this question is not platform specific-specific) and am confused/surprised regarding the computational complexity (execution time) of mbedtls_rsa_pkcs1_sign()mbedtls_rsa_pkcs1_sign() versus mbedtls_rsa_pkcs1_verify()mbedtls_rsa_pkcs1_verify(). Apparently the _sign is much more computationally complex than the _verify. I don't understand this, and would expect the opposite to be true.

Observations: mbedtls_rsa_pkcs1_decrypt() or mbedtls_rsa_pkcs1_sign() < 3 secs mbedtls_rsa_pkcs1_encrypt() or mbedtls_rsa_pkcs1_verify() < 100 millisecs (this is for RSA-2048 / SHA-256)

  • mbedtls_rsa_pkcs1_decrypt() or mbedtls_rsa_pkcs1_sign() < 3 secs
  • mbedtls_rsa_pkcs1_encrypt() or mbedtls_rsa_pkcs1_verify() < 100 millisecs (this is for RSA-2048 / SHA-256)

I would have assumed that the verify should be similar in complexity to the decrypt (because it requires a decryption of the signature hash), and that the sign would be similar in complexity to encrypt (because it requires an encryption of the hash). I understand that for the signature operations the Private and Public key use is reversed, but I'm not sure how/why that effectsaffects things.

I've been experimenting with MBEDTLS on an ARM-M4 (but this question is not platform specific) and am confused/surprised regarding the computational complexity (execution time) of mbedtls_rsa_pkcs1_sign() versus mbedtls_rsa_pkcs1_verify(). Apparently the _sign is much more computationally complex than the _verify. I don't understand this, and would expect the opposite to be true.

Observations: mbedtls_rsa_pkcs1_decrypt() or mbedtls_rsa_pkcs1_sign() < 3 secs mbedtls_rsa_pkcs1_encrypt() or mbedtls_rsa_pkcs1_verify() < 100 millisecs (this is for RSA-2048 / SHA-256)

I would have assumed that the verify should be similar in complexity to the decrypt (because it requires a decryption of the signature hash), and that the sign would be similar in complexity to encrypt (because it requires an encryption of the hash). I understand that for the signature operations the Private and Public key use is reversed, but I'm not sure how/why that effects things.

I've been experimenting with MBEDTLS on an ARM-M4 (but this question is not platform-specific) and am confused/surprised regarding the computational complexity (execution time) of mbedtls_rsa_pkcs1_sign() versus mbedtls_rsa_pkcs1_verify(). Apparently the _sign is much more computationally complex than the _verify. I don't understand this and would expect the opposite to be true.

Observations:

  • mbedtls_rsa_pkcs1_decrypt() or mbedtls_rsa_pkcs1_sign() < 3 secs
  • mbedtls_rsa_pkcs1_encrypt() or mbedtls_rsa_pkcs1_verify() < 100 millisecs (this is for RSA-2048 / SHA-256)

I would have assumed that the verify should be similar in complexity to the decrypt (because it requires decryption of the signature hash) and that the sign would be similar in complexity to encrypt (because it requires encryption of the hash). I understand that for the signature operations the Private and Public key use is reversed, but I'm not sure how/why that affects things.

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Aloysius Parker
Aloysius Parker
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RSA PKCS#1 v.15 Signature verification computational complexity explanation?

I've been experimenting with MBEDTLS on an ARM-M4 (but this question is not platform specific) and am confused/surprised regarding the computational complexity (execution time) of mbedtls_rsa_pkcs1_sign() versus mbedtls_rsa_pkcs1_verify(). Apparently the _sign is much more computationally complex than the _verify. I don't understand this, and would expect the opposite to be true.

Observations: mbedtls_rsa_pkcs1_decrypt() or mbedtls_rsa_pkcs1_sign() < 3 secs mbedtls_rsa_pkcs1_encrypt() or mbedtls_rsa_pkcs1_verify() < 100 millisecs (this is for RSA-2048 / SHA-256)

I would have assumed that the verify should be similar in complexity to the decrypt (because it requires a decryption of the signature hash), and that the sign would be similar in complexity to encrypt (because it requires an encryption of the hash). I understand that for the signature operations the Private and Public key use is reversed, but I'm not sure how/why that effects things.