A bundle has 4 transactions:

  • The output; address and amount of IOTA recipient gets.
  • The input; address, and amount of IOTA sender gives, and half of their signature.
  • The other half of the sender's signature.
  • Remaining ouput; if there is left over funds, you have to send it to your own address because IOTA address cannot be spent twice.

A transaction is 2673 trytes, signatureMessageFragment (more info here) has a size of 2187 trytes, and an IOTA signature's length = security * 2187 trytes.

If I am using security = 1, then my signature is exactly the size of signatureMessageFragment.

Does that mean I can tranfer IOTA in a bundle with only 3 transactions?

1 Answer 1


Yes, you are right.

In case of security = 1 and you are spending all the funds on one address (with no change needed), you can even get away with only 2 transactions (one with the input and sig, and one with the output).

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