D is a hint for roman numeral 500. There are a lot of 4 in that string and if you look closely you’ll notice that every third number is a 4. Make groups of 3

417 415 433 444 443 449 449 443 419 415

From 500 subtract each numbers

83 85 67 56 57 51 51 57 81 85

We now have a good Ascii range, convert decimal to Ascii

SUC89339QU

Now we need the keyword, the operation we used to get those numbers was 500 LESS the numbers

suc89less339qu

Let’s start by isolating the numbers that the letters are splitting

343 0 343 512 343 64 125 1 125 343 125 64 125 125 125 1 343 729 512 0

Find cubic root of every numbers

7 0 7 8 7 4 5 1 5 7 5 4 5 5 5 1 7 9 8 0

Make pairs

70 78 74 51 57 54 55 51 79 80

Convert decimal to Ascii

FNJ39673OP

To get those they use a power of three or powercube

fnj39powercube673op

For the second passcode, take the letters of the string

bskfixqerxqghglijyi

Did I say 3 was the best hint for this code ? Rot -3

yphcfunboundedifgvf

Convert letters to numbers using a=0 where numbers should fall

yph25unbounded856vf