# Effect of scaleModSize on Multiplication

**URL:** <https://openfhe.discourse.group/t/effect-of-scalemodsize-on-multiplication/1949>\
**Category:** FHE Questions\
**Created:** [March 20, 2025, 10:31pm UTC](https://openfhe.discourse.group/t/effect-of-scalemodsize-on-multiplication/1949 "2025-03-20T22:31:58Z")\
**Posts on this page:** 1\
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**Author:** ![andreea.alexandru](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/andreea.alexandru/32/378_2.png) [@andreea.alexandru](https://openfhe.discourse.group/u/andreea.alexandru)\
**Post date:** [March 21, 2025, 8:30pm UTC](https://openfhe.discourse.group/t/effect-of-scalemodsize-on-multiplication/1949/2 "2025-03-21T20:30:40Z")

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The default firstModSize is 60 bits. When you set scaleModSize to 59 bits and no extra moduli, you leave very little space for the message to be decrypted.

To obtain correct decryption, the expected magnitude of the messages to be decrypted should fit into firstModSize - scaleModSize bits (or otherwise, leave an extra modulus).

Please see the forum posts linked in this thread [Crashes when firstModSize and scalingModSize are equal in CKKS - #2 by andreea.alexandru](https://openfhe.discourse.group/t/crashes-when-firstmodsize-and-scalingmodsize-are-equal-in-ckks/1287/2) for further explanations.

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