Reply To: Extracurricular challenges

19th November 2025 at 11:30 am #113626

upsidedown

Participant

Second cipher: upsidedown-2025-2

5×5 matrix (mod 31), this matrix is keyed with a multi-word phrase from my favourite film, with a constant vector (size 5) added to each block BEFORE encryption. Alphabet: ABCDEFGHIJKLMNOPQRSTUVWXYZ09:._ (ditto for underscore character)

If you’ve watched my favourite film you might be able to derive some cribs from the selection of symbols included in the alphabet.


KENMTZF9NM9EVTSUSSQHO_.SUQYEEGIODJZOKMSV:ISDOKN0ZSLQNK.IYOKOGACFTHMROILKNNR
IVC9IRSWGDQ:J0ZWNENQJMWWKBKSAF:ISDOKN0ZSTUNW.FR.F0VMW:0P_TKNEP:XMMXFUROMY.M
XN9PB9AEFQBJ9UMBCFTTQBBPLEBTSKIJZWOX0QS:WBCYCKHE0QMZOOFUIAKW_DJTD:ISDOKN0ZS
MU0ZM_FGIXHUQKLHY0DRRI9TMJDHJDGOB.TJDFX.9BXOUTTLC.XGRWBIYOKOF0N:MFUNTQPJNDM
FR.F0J.ICT0B.DOJWHE0RD.MKAGFFUT:D:LHAADGISEQEI9EXH.I.0NIOUVTWOUSV9KGURPBXTA
AS9O9GWK.RLP0AZHHAAPULMR_VQVZCX.UBMYQ:FGBRZWGHKHIP0CCMF9AISQLU0__PNJKPL9PHY
VQZHHNCNKMIZEOUPQDHV:YNVFDYPYNTTLC.EURXI_IEGCREUKHKCPQ.PVI0.U9RZ:JZPPFSDLQ.
GDPTJKSPRONEKQUD_PHZBT9XAE.OGEFNQHKDEOSVMAMPCKDGAMZNCJSV.WBR:.ZVUBELOLPJNDM
RZ:C..XCSXY.R:L9TAKEJWFQGPFRWZ9FK9O.TVZB0_0__MUTLKDR0J.LL9GGKP.RKMCO_LNFWCU
MSGBNHVQ.0FJSQVPNF_RGCX_GIHT:ZPUNG:VIHKXUOPGG.ZB.OM_Q0NUGUTOTP.BNU_GJGVMXKC
UQVSNGPKV_FWWDY9NU:SKRBBDXEOKC_JLD.VOOMFBKHOLI9BQ_SLIWDXMKG_XTOE0EL_PDQ9GXU
FWDTTGFVIUDZJQ0QNCDGLSFM:IMKNUN.KGOC_XFPGY_XZCVHWPSDLQ.GDPTJF.M.ALDSRTBR.P:
ENOLINMBQZTF.GLKGRPZXTMSQSVAEGWGVT:LD0:LLO.MGIKYYWSDQRXNOFUFCVQ9:_IUCODMELM
V:NYIKQTXLYW9YWZ9::FXYPU.LMD_PTEVS9EBD.S0VG9.PNJKPNQGCY9DDEU

As before, I have a program which solves this in under two minutes.