Actually, RSASSA-PKCS1-v1_5 padding is quite simple, and has no known weaknesses for signatures. (It is broken for encryption unless implemented in a very very careful way.)

The padding format is:

00 01 FF FF FF ... FF FF 00 <DER of Hash Type> <Hash>

where DER of Hash Type is a byte string that depends on the type of hash you used, and Hash is the output of the hash function. For SHA-256, the DER is the byte string:

30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20

So, you take your hash, prepend it with a fixed string, and you're done.

If you want to make things a bit simpler, you could omit the DER of Hash Type (which would mean that you're not precisely PKCS #1.5, however it does not introduce any known weaknesses.

Actually, RSASSA-PKCS1-v1_5 signature padding is quite simple, and has no known weaknesses (the similarly named RSAES-PKCS1-v1_5 padding is broken for encryption unless implemented in a very very careful way; don't use that).

The padding format is:

00 01 FF FF FF ... FF FF 00 <DER of Hash Type> <Hash>

where DER of Hash Type is a byte string that depends on the type of hash you used, and Hash is the output of the hash function. For SHA-256, the DER is the byte string:

30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20

So, you take your hash, prepend it with a fixed string, and you're done.

If you want to make things a bit simpler, you could omit the DER of Hash Type (which would mean that you're not precisely PKCS #1.5, however it does not introduce any known weaknesses.

Actually, RSASSA-PKCS1-v1_5 padding is quite simple, and has no known weaknesses.

The padding format is:

00 01 FF FF FF ... FF FF 00 <DER of Hash Type> <Hash>

where DER of Hash Type is a byte string that depends on the type of hash you used, and Hash is the output of the hash function. For SHA-256, the DER is the byte string:

30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20

So, you take your hash, prepend it with a fixed string, and you're done.

If you want to make things a bit simpler, you could omit the DER of Hash Type (which would mean that you're not precisely PKCS #1.5, however it does not introduce any known weaknesses.

Actually, RSASSA-PKCS1-v1_5 padding is quite simple, and has no known weaknesses for signatures. (It is broken for encryption unless implemented in a very very careful way.)

The padding format is:

00 01 FF FF FF ... FF FF 00 <DER of Hash Type> <Hash>

where DER of Hash Type is a byte string that depends on the type of hash you used, and Hash is the output of the hash function. For SHA-256, the DER is the byte string:

30 31 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20

So, you take your hash, prepend it with a fixed string, and you're done.

If you want to make things a bit simpler, you could omit the DER of Hash Type (which would mean that you're not precisely PKCS #1.5, however it does not introduce any known weaknesses.