One-time pad/Phix

Phix

---

A simple xor-based one time pad that allows any file to be encrypted and decrypted, since it seems silly to limit this to plaintext. The one time pad files are therefore binary rather than plain text, with comments and used counts in separate .1te/.1td files, rather than #/- in the .1tp itself. Uses a trivial xor rather than a Vigenere cipher, since the latter adds nothing. Ignores the "true random numbers, eg from /dev/random" part, especially since the wikipedia page cites /dev/random as potentially unsuitable for cryptographic use. Instead this just uses the builtin rand(): for better security I might suggest you replace that, possibly with several different (pseudo) random number generators.

The dump feature is only for testing, obviously, as is decrypt defaulting to the last encrypted message/file/pad. Note however that .1te/.1td handling is not: if you try to make a one time pad "bi-directional", then not only would there be some confusion and re-alignment issues should both parties send a message at the same time, but two messages encrypted with the same part of the one time pad severely weakens the security of those two messages. To prevent that, delete/do not share the .1te or .1td file, and it will not allow encryption/decryption respectively.

Note that options 4 (Encrypt plain text) and 5 (Decrypt cipher text) are also only suitable for testing: you cannot actually enter anything for option 5, it just decodes whatever was last encoded by option 4, however it would be trivial to store the output of option 4 in a file and send that, and the recipient would then decode it using option 7 (Decrypt file).

TIP: if a message gets lost, or you quit without decrypting something, then edit the recipient's .1td file manually, so that Used matches the sender's .1te file. <lang Phix>string default_enc = "",

      default_dec = ""

function size_used(string name, integer now_used=0)

   object txt = read_lines(name)
   if sequence(txt) then
       integer size, used
       for i=1 to length(txt) do
           if match("Size",txt[i])=1 then
               Template:Size = scanf(txt[i],"Size: %d")
           elsif match("Used",txt[i])=1 then
               if now_used=0 then
                   Template:Used = scanf(txt[i],"Used: %d")
                   return {size,used}
               else
                   txt[i] = sprintf("Used: %d",now_used)
                   if not write_lines(name,txt) then
                       printf(1,"error updating %s\n",{name})
                   end if
                   return 1
               end if
           end if
       end for
   end if
   return {-1,-1}

end function

procedure list_one_time_pads(bool set_default=false)

   puts(1,"\n")
   sequence d = dir("*.1t?")
   if d={} then
       printf(1,"No one time pad files found.\n")
       return
   elsif set_default then
       sequence bases = {},
                types = {{},{},{}}     -- p/e/d
       for i=1 to length(d) do
           string name = d[i][D_NAME]
           integer dot = find('.',name)
           if dot!=0 then
               string base = name[1..dot-1],
                      ext = name[dot+1..$]
               integer e = find(ext,{"1tp","1te","1td"})
               if e!=0 then
                   integer k = find(base,bases)
                   if k=0 then
                       bases = append(bases,base)
                       k = length(bases)
                   end if
                   types[e] &= k
               end if
           end if
       end for
       default_enc = iff(length(types[2])=1?bases[types[2][1]]&".1te":"")
       default_dec = iff(length(types[3])=1?bases[types[3][1]]&".1td":"")
   else
       for i=1 to length(d) do
           sequence di = d[i]
           string name = di[D_NAME],
                  info = iff(name[$]='p'?sprintf("Size: %d",di[D_SIZE])
                        :sprintf("Size: %d, Used: %d",size_used(name)))
           printf(1,"%s  Created: %02d/%02d/%04d, %s\n",
                    {name,di[D_DAY],di[D_MONTH],di[D_YEAR],info})
       end for
   end if

end procedure

procedure dump_hex(sequence s)

   if length(s)=0 then
       printf(1,"{}\n")
   else
       for i=1 to length(s) do
           printf(1,"%02x%c",{s[i],iff(mod(i,16)=0?'\n':' ')})
       end for
   end if

end procedure

procedure dump_file(string file, bool ashex=false)

   printf(1,"The contents of %s:\n\n",{file})
   if match(".1tp",file) or ashex then
       integer fn = open(file,"rb")
       dump_hex(get_bytes(fn, 64))
       close(fn)
       puts(1,iff(get_file_size(file)>64?"...\n\n","\n"))
   else
       puts(1,join(read_lines(file),"\n")&"\n")
   end if

end procedure

procedure create_one_time_pad()

   string filename = prompt_string("OTP file name to create (without extension):")
   if find('.',filename) then
       puts(1,"extension not allowed\n")
   elsif filename!="" then
       string pfile = filename&".1tp",
              efile = filename&".1te",
              dfile = filename&".1td"
       if file_exists(pfile) then
           string del = lower(prompt_string("File already exists - delete?:"))
           if not find(del,{"y","yes"}) then return end if
           if not delete_file(pfile) then
               printf(1,"error deleting %s\n",{pfile})
               return
           end if
       end if
       string comment = prompt_string("comment (optional):")
       integer filesize
       while 1 do
           string sizestr = prompt_string("file size (1MB):")
           sequence res = iff(sizestr=""?Template:1,"MB":scanf(sizestr,"%d%s"))
           if length(res)=1 then
               integer k = find(upper(res[1][2]),{"","K","KB","M","MB","G","GB"})
               if k!=0 then
                   k = {1,1024,1024*1024,1024*1204}[floor(k/2)+1]
                   filesize = res[1][1]*k
                   exit
               end if
               printf(1,"unknown suffix:%s - use K|M|G or KB|MB|GB\n",{res[1][2]})
           end if
       end while
       printf(1,"Creating %s (%d bytes)\n",{pfile,filesize})
       integer fn = open(pfile,"wb")
       if fn=-1 then
           printf(1,"error opening %s\n",{pfile})
           return
       end if
       for i=1 to filesize do
           puts(fn,rand(256)-1)
       end for
       close(fn)
       fn = open(efile,"w")
       if fn=-1 then
           printf(1,"error opening %s\n",{efile})
           return
       end if
       printf(fn,"# OTP file\n# %s\nSize: %d\nUsed: 0\n",{comment,filesize})
       close(fn)
       if not copy_file(efile,dfile,true) then
           printf(1,"error copying %s to %s\n",{efile,dfile})
           return
       end if
       printf(1,"\n%s and %s and %s have been created in the current directory.\n\n",
                {pfile,efile,dfile})
       dump_file(pfile)
       dump_file(efile)
       default_enc = efile
       default_dec = dfile
   end if

end procedure

procedure delete_one_time_pad()

   string filename = prompt_string("OTP file name to delete (without extension):")
   if find('.',filename) then
       puts(1,"extension not allowed\n")
   elsif filename!="" then
       string efile = filename&".1te",
              dfile = filename&".1td"
       filename &= ".1tp"
       if not file_exists(filename) then
           printf(1,"file %s found\n",{filename})
           return
       end if
       string del = lower(prompt_string("Delete file - are you sure?:"))
       if not find(del,{"y","yes"}) then
           printf(1,"file not deleted\n")
           return
       end if
       if not delete_file(filename) then
           printf(1,"error deleting %s\n",{filename})
           return
       end if
       integer c = 1
       c += delete_file(efile)
       c += delete_file(dfile)
       printf(1,"%d file%s successfully deleted.\n",{c,iff(c=1?"":"s")})
       if default_enc=efile then default_enc = "" end if
       if default_dec=dfile then default_dec = "" end if
   end if

end procedure

sequence msg = {}

procedure crypt_text(integer de)

   sequence text = iff(de='d'?msg:prompt_string("message:"))
   string dflt = iff(de='d'?default_dec:default_enc),
          otp = iff(length(dflt)?"OTP ("&dflt&"):":"OTP:"),
          efile = prompt_string(otp)
   if efile="" then efile=dflt end if
   if length(efile) then
       if not find('.',efile) then efile &= ".1t"&de end if
       integer {size,used} = size_used(efile)
       if size=-1 or used=-1 then
           printf(1,"File %s cannot be opened\n",{efile})
       elsif used+length(text)>size then
           printf(1,"OTP exhausted (%d>%d)\n",{used+length(text),size})
       else
           efile[$] = 'p'
           integer fn = open(efile,"rb")
           if seek(fn,used)!=SEEK_OK then
               printf(1,"Error in seek(%s,%d)\n",{efile,fn})
               text = ""
           else    
               msg = get_bytes(fn,length(text))
               msg = sq_xor_bits(msg,text)
               if de='e' then
                   printf(1,"Encrypted:\n")
                   dump_hex(msg)
                   printf(1,"\n\n")
               else
                   printf(1,"Decrypted: %s\n\n",{msg})
               end if
           end if
           close(fn)
           efile[$] = de
           if length(text)!=0 then
               {} = size_used(efile, used+length(text))
           end if
           dump_file(efile)
       end if
   end if

end procedure

string last_file = ""

procedure crypt_file(integer de)

   string file = iff(de='d' and last_file!=""?"file ("&last_file&"):":"file:"),
          filename = prompt_string(file)
   if de='d' and filename="" then filename=last_file end if
   if filename="" then return end if
   if not file_exists(filename) then
       printf(1,"The file %s does not exist\n",{filename})
       return
   end if
   atom filesize = get_file_size(filename)
   integer fn = open(filename,"rb")
   if fn=-1 then
       printf(1,"error opening %s\n",{filename})
       return
   end if
   sequence bytes = get_bytes(fn,filesize)
   close(fn)
   if length(bytes)!=filesize then ?9/0 end if -- uh?
   if de='e' then
       dump_file(filename, true)
   end if
   string outfile = prompt_string("output:")
   if length(outfile)=0 then return end if
   integer outfn = open(outfile,"wb")
   if outfn=-1 then
       printf(1,"error opening output file %s\n",{outfile})
       return
   end if
   string dflt = iff(de='d'?default_dec:default_enc),
          otp = iff(length(dflt)?"OTP ("&dflt&"):":"OTP:"),
          efile = prompt_string(otp)
   if efile="" then efile=dflt end if
   if length(efile) then
       if not find('.',efile) then efile &= ".1t"&de end if
       integer {size,used} = size_used(efile)
       if size=-1 or used=-1 then
           printf(1,"File %s cannot be opened\n",{efile})
       elsif used+filesize>size then
           printf(1,"OTP exhausted (%d>%d)\n",{used+filesize,size})
       else
           efile[$] = 'p'
           fn = open(efile,"rb")
           if seek(fn,used)!=SEEK_OK then
               printf(1,"Error in seek(%s,%d)\n",{efile,fn})
               filesize = 0
           else    
               msg = get_bytes(fn,filesize)
               msg = sq_xor_bits(msg,bytes)
               puts(outfn,msg)
           end if
           close(fn)
           close(outfn)
           efile[$] = de
           if filesize!=0 then
               {} = size_used(efile, used+filesize)
           end if
           if de='d' then
               dump_file(outfile, true)
           else
               last_file = outfile
           end if
           dump_file(efile)
       end if
   end if

end procedure

list_one_time_pads(set_default:=true)

-- note: the trailing space after the opening """ is deliberate: constant menu_txt = """ 1. List one time pad files. 2. Create one time pad file. 3. Delete one time pad file. 4. Encrypt plain text. 5. Decrypt cipher text. 6. Encrypt file. 7. Decrypt file. 8. Quit program. Your choice (1 to 8) : """

while 1 do

   integer choice = prompt_number(menu_txt,{1,8})
   switch choice do
       case 1: list_one_time_pads()
       case 2: create_one_time_pad()
       case 3: delete_one_time_pad()
       case 4: crypt_text('e')
       case 5: crypt_text('d')
       case 6: crypt_file('e')
       case 7: crypt_file('d')
       case 8: exit
       default :puts(1,"not implemented...\n")
   end switch

end while</lang>

Output:

Sample session. Similar to Kotlin, menu display/selection has been shorted to <menu N. Xxxx.>

No one time pad files found.

1. List one time pad files.
2. Create one time pad file.
3. Delete one time pad file.
4. Encrypt plain text.
5. Decrypt cipher text.
6. Encrypt file.
7. Decrypt file.
8. Quit program.
Your choice (1 to 8) : 2
OTP file name to create (without extension):007
comment (optional):Pussy Galore
file size (1MB):
Creating 007.1tp (1048576 bytes)

007.1tp and 007.1te and 007.1td have been created in the current directory.

The contents of 007.1tp:

C3 A1 90 B2 70 E6 A2 DD 27 F4 3C 21 48 D1 54 1C
D7 7E AA 09 40 CC 49 83 F4 E3 96 86 1D 48 15 F6
A3 C2 5F 47 00 BE D1 6B 4E 4A EA 50 DB F8 62 2F
D5 66 D5 0F A9 63 E6 4D 65 BB 67 70 6F 51 34 73
...

The contents of 007.1te:

# OTP file
# Pussy Galore
Size: 1048576
Used: 0

<menu 1. List one time pad files.>
007.1td  Created: 10/11/2018, Size: 1048576, Used: 0
007.1te  Created: 10/11/2018, Size: 1048576, Used: 0
007.1tp  Created: 10/11/2018, Size: 1048576

<menu 4. Encrypt plain text.>
message:This is message 1234
OTP (007.1te):
Encrypted:
97 C9 F9 C1 50 8F D1 FD 4A 91 4F 52 29 B6 31 3C
E6 4C 99 3D

The contents of 007.1te:

# OTP file
# Pussy Galore
Size: 1048576
Used: 20

<menu 5. Decrypt cipher text.>
OTP (007.1td):
Decrypted: This is message 1234

The contents of 007.1td:

# OTP file
# Pussy Galore
Size: 1048576
Used: 20

<menu 8. Quit program.>