The Codex Igo is a handwritten book owned by the British Library in London (Sloane 1360). It is completely encrypted. However, the encryption is easy to solve because it consists only of letter substitution. The Codex Igo has about 460 pages. The following picture is a facsimile of page 3. For copyright reasons I can’t publish any original page. If you are interested in getting scans of the whole book, please contact me.

Armin Krauß, a German computer expert and codebreaker, has decrypted a number of pages of the Codex Igo. Here are the results (published with his permission):

0005:
The 3 peticion x
jhus jhus jhus
strength me
jhus strengh me in
soule and body to
excecut the workes
of vertu to the
pleasure of thee

0006:
where by i may con
to the ever lasting
joy and filicite
graunt me firme
purpose most mer=
cyfull jhesu to a
mend me life ad
to recompence for

0007:
those yeres which
i have mispent to
the displeasure of
thee in evell thou=
ghts delectacions
consentings words
workes and evell
costomes also in

0008:
breking thy com=
maundementes
whereby i have
deservid danacins
and thyne enimite
make mine hart
obedient to fulfill
thy will and redy to

0009:
do for thy love
thy worses of pite
graunt me the seven
gistes of the holy
gost the eight
leatitudes the four
cardinall vertues
ad in receving of

0010:
thy sacramentes
devoutly dispos me
have mercy on all
the 4 peticion x
ihus ihus ihus
comfort me
ihus comfort me
and geve me grace

0011:
to have my most
joy and pleasure in
thee. send me he=
avenly meditaci=
ons gostly swetnes
and verfor of thy
glory ravish my

0012:
soule w bren=
ning desier
to the heavenly
ivi where i
shall everlasting=
ly dwell with
thee graunt me

0013:
swet savior ihus
contempt of all
damnable pleasure
full of sinne and
misery graunt
me remembrance
of my salvacion

0014:
wt feare of damnacion
also remembrance
of thy goodnes thy
geftis and great
kindnes shewed
to me reduce in
to my foule mind

0015:
my sinnes and un=
kindnes wherby
i have offendid
thee graunt me the
sprit of perfit pe
naunce contricion
confession and

0016:
satisfaccion to
obtaine thy grace
and fro filthy sinne
to pourg me
have mercy on all
The 5 peticion x
ihus ihus ihus make
me constant and stable

0017:
ihus make me con=
stant and stable in
faith hope and cha=
rite wt continuance
in vertu and will not
to offend thee make
me oft to re=
member thy passion

0018:
and bitter paines
which thou sof=
frest for me send
me perfet paci=
ens in all tribu=
lacion and as ver=
site preserve

0019:
me from prid yer
enui covetis and
from all offencis
to thy lav contrary
the catholike ob=
servantes of thy
church make me

0020:
to kepe truly
make my soule
to holy doctrine
obedient and to the
thinges perti=
ning to my gost=
ly werke for the

0021:
love of thee suf=
fer no false delit
of this decevable
life by fleshly ten=
tacion and fraud
of the find for to
blind me: to the

0022:
houre of my death
my five wittes
ihesu kepe i be=
sech thee from
exses in speaking
in feding and wor
king preserve
my frailte

0023:
have mercy on all
The 6 peticion x
Deus(?) noster in nome(?)
ihus ihus ihus light me
ihus light me with
gostly wisdom to
know thy goodnes

0024:
and those thinges
which are most
acceptable to thee
graunt me grace
to geve good
ensample to soules
profitable that

0025:
non me hourte
by me to helpe
those wt good coun=
saill which have
offendid thee make
me to proced from
vertu to vertu

0026:
unto such time that
i shall clerely see
thy mageste leate
me not tourne to
those sinnes which
i have soroid for
and by confession

0027:
have accusid me of
the horrable sentence
of endles death the
terreble iudment
of dannacion thy wr=
ath ire and inding=
nacion mercyfull

0028:
lord let never fall
upon me thy mercy
and thy merites my
saviour ever be
betwene them and me
have mercy on all
The 7 peticion x

0029:
ihus ihus ihus graunt
me grace to dread thee
ihus graunt me grace
inwardly to dread thee
and to eschu those
thinges where by
i might offend thee

0030:
the blessed mother
be mediatrice for
me and purchace me
a contrite harte for
that i have offendid
thee remove my
sinfull disposcissions

0031:
which dull mine
hart as .ead as suppres
me: all thy saintes
pray for me that i
be not seperat from
thee and there blessed
felowship in the

0032:
heavenly citie
let me not for
geat good lord the
riches of thy good=
nes of thy pacience
of thy long suffe=
ring and benignite
let the threatning

0033:
of paine and torment
which shall fill upon
sinners the lose of the
love and of thy hea=
venly inheritaunce
ever feare me to
offend thee suffer

0092:
In nomine Jhesu omne
genuflectatus celestius
terrestrius et infernorum
et omnis lingua
confiteantur quia
dus Jesus christus in
gloria est dei patris
~~~ amen ~~~

0093:
dus noster Jhesus
christus humilianit
semetipsum pro nobis
factus obediens
.sque ad mortem
mortem antes crucis
~~~ amen ~~~

0094:
primus querite
regnum dei
postia omnia
adicietur lobis
~~~ laus de. ~~~
diligam fedue
MVSEVM
BRITAN
NICUM

0185:
mihi .. abscandalis
opancion in iguitates ~~
tadent in reriaculo
eios peccatores singu=
lariter sun ego donec
transeam ~~~~~
~~ gloria ~~
voce mea ad deum