diff --git a/mmgen/addrfile.py b/mmgen/addrfile.py
index d5a8770d..956b3307 100755
--- a/mmgen/addrfile.py
+++ b/mmgen/addrfile.py
@@ -26,8 +26,6 @@ from .util import (
 	qmsg_r,
 	die,
 	capfirst,
-	get_lines_from_file,
-	write_data_to_file,
 	keypress_confirm,
 )
 from .protocol import init_proto
@@ -74,6 +72,7 @@ class AddrFile(MMGenObject):
 
 	def write(self,fn=None,ask_tty=True,ask_write_default_yes=False,binary=False,desc=None):
 		from .opts import opt
+		from .fileutil import write_data_to_file
 		write_data_to_file(
 			fn or self.filename,
 			self.fmt_data,
@@ -224,6 +223,7 @@ class AddrFile(MMGenObject):
 			return ( proto, proto.addr_type(mmtype_key) )
 
 		p = self.parent
+		from .fileutil import get_lines_from_file
 		lines = get_lines_from_file(fn,p.desc+' data',trim_comments=True)
 
 		try:
diff --git a/mmgen/crypto.py b/mmgen/crypto.py
index 947c6426..91cfc0dd 100755
--- a/mmgen/crypto.py
+++ b/mmgen/crypto.py
@@ -232,6 +232,7 @@ def get_hash_preset_from_user(hp=g.dfl_hash_preset,desc='data'):
 def get_new_passphrase(desc,passchg=False):
 	pw_desc = f"{'new ' if passchg else ''}passphrase for {desc}"
 	if opt.passwd_file:
+		from .fileutil import get_words_from_file
 		pw = ' '.join(get_words_from_file(opt.passwd_file,pw_desc))
 	elif opt.echo_passphrase:
 		pw = ' '.join(get_words_from_user(f'Enter {pw_desc}: '))
@@ -254,6 +255,7 @@ def get_new_passphrase(desc,passchg=False):
 def get_passphrase(desc,passchg=False):
 	pw_desc = f"{'old ' if passchg else ''}passphrase for {desc}"
 	if opt.passwd_file:
+		from .fileutil import get_words_from_file
 		pwfile_reuse_warning(opt.passwd_file)
 		return ' '.join(get_words_from_file(opt.passwd_file,pw_desc))
 	else:
diff --git a/mmgen/data/version b/mmgen/data/version
index c400957f..28601de0 100644
--- a/mmgen/data/version
+++ b/mmgen/data/version
@@ -1 +1 @@
-13.1.dev006
+13.1.dev007
diff --git a/mmgen/fileutil.py b/mmgen/fileutil.py
new file mode 100755
index 00000000..da7b3d78
--- /dev/null
+++ b/mmgen/fileutil.py
@@ -0,0 +1,313 @@
+#!/usr/bin/env python3
+#
+# mmgen = Multi-Mode GENerator, command-line Bitcoin cold storage solution
+# Copyright (C)2013-2022 The MMGen Project <mmgen@tuta.io>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+fileutil.py: Routines that read, write, execute or stat files
+"""
+
+import sys,os
+
+from .globalvars import g
+from .exception import FileNotFound,MaxInputSizeExceeded
+from .util import (
+	msg,
+	qmsg,
+	dmsg,
+	die,
+	confirm_or_raise,
+	get_extension,
+	is_utf8,
+	capfirst,
+	make_full_path,
+	strip_comments,
+	keypress_confirm,
+)
+
+def check_or_create_dir(path):
+	try:
+		os.listdir(path)
+	except:
+		if os.getenv('MMGEN_TEST_SUITE'):
+			from subprocess import run
+			try: # exception handling required for MSWin/MSYS2
+				run(['/bin/rm','-rf',path])
+			except:
+				pass
+		try:
+			os.makedirs(path,0o700)
+		except:
+			die(2,f'ERROR: unable to read or create path {path!r}')
+
+def check_binary(args):
+	from subprocess import run,DEVNULL
+	try:
+		run(args,stdout=DEVNULL,stderr=DEVNULL,check=True)
+	except:
+		rdie(2,f'{args[0]!r} binary missing, not in path, or not executable')
+
+def shred_file(fn,verbose=False):
+	check_binary(['shred','--version'])
+	from subprocess import run
+	run(
+		['shred','--force','--iterations=30','--zero','--remove=wipesync']
+		+ (['--verbose'] if verbose else [])
+		+ [fn],
+		check=True )
+
+def _check_file_type_and_access(fname,ftype,blkdev_ok=False):
+
+	import stat
+
+	access,op_desc = (
+		(os.W_OK,'writ') if ftype in ('output file','output directory') else
+		(os.R_OK,'read') )
+
+	if ftype == 'output directory':
+		ok_types = [(stat.S_ISDIR, 'output directory')]
+	else:
+		ok_types = [
+			(stat.S_ISREG,'regular file'),
+			(stat.S_ISLNK,'symbolic link')
+		]
+		if blkdev_ok:
+			ok_types.append((stat.S_ISBLK,'block device'))
+
+	try:
+		mode = os.stat(fname).st_mode
+	except:
+		raise FileNotFound(f'Requested {ftype} {fname!r} not found')
+
+	for t in ok_types:
+		if t[0](mode):
+			break
+	else:
+		ok_list = ' or '.join( t[1] for t in ok_types )
+		die(1,f'Requested {ftype} {fname!r} is not a {ok_list}')
+
+	if not os.access(fname,access):
+		die(1,f'Requested {ftype} {fname!r} is not {op_desc}able by you')
+
+	return True
+
+def check_infile(f,blkdev_ok=False):
+	return _check_file_type_and_access(f,'input file',blkdev_ok=blkdev_ok)
+
+def check_outfile(f,blkdev_ok=False):
+	return _check_file_type_and_access(f,'output file',blkdev_ok=blkdev_ok)
+
+def check_outdir(f):
+	return _check_file_type_and_access(f,'output directory')
+
+def get_seed_file(cmd_args,nargs,invoked_as=None):
+
+	from .opts import opt
+	from .filename import find_file_in_dir
+	from .wallet import MMGenWallet
+
+	wf = find_file_in_dir(MMGenWallet,g.data_dir)
+
+	wd_from_opt = bool(opt.hidden_incog_input_params or opt.in_fmt) # have wallet data from opt?
+
+	import mmgen.opts as opts
+	if len(cmd_args) + (wd_from_opt or bool(wf)) < nargs:
+		if not wf:
+			msg('No default wallet found, and no other seed source was specified')
+		opts.usage()
+	elif len(cmd_args) > nargs:
+		opts.usage()
+	elif len(cmd_args) == nargs and wf and invoked_as != 'gen':
+		qmsg('Warning: overriding default wallet with user-supplied wallet')
+
+	if cmd_args or wf:
+		check_infile(cmd_args[0] if cmd_args else wf)
+
+	return cmd_args[0] if cmd_args else (wf,None)[wd_from_opt]
+
+def _open_or_die(filename,mode,silent=False):
+	try:
+		return open(filename,mode)
+	except:
+		die(2,'' if silent else
+			'Unable to open file {!r} for {}'.format(
+				({0:'STDIN',1:'STDOUT',2:'STDERR'}[filename] if type(filename) == int else filename),
+				('reading' if 'r' in mode else 'writing')
+			))
+
+def write_data_to_file( outfile,data,desc='data',
+						ask_write=False,
+						ask_write_prompt='',
+						ask_write_default_yes=True,
+						ask_overwrite=True,
+						ask_tty=True,
+						no_tty=False,
+						quiet=False,
+						binary=False,
+						ignore_opt_outdir=False,
+						check_data=False,
+						cmp_data=None):
+
+	from .opts import opt
+
+	if quiet:
+		ask_tty = ask_overwrite = False
+
+	if opt.quiet:
+		ask_overwrite = False
+
+	if ask_write_default_yes == False or ask_write_prompt:
+		ask_write = True
+
+	def do_stdout():
+		qmsg('Output to STDOUT requested')
+		if g.stdin_tty:
+			if no_tty:
+				die(2,f'Printing {desc} to screen is not allowed')
+			if (ask_tty and not opt.quiet) or binary:
+				confirm_or_raise('',f'output {desc} to screen')
+		else:
+			try:    of = os.readlink(f'/proc/{os.getpid()}/fd/1') # Linux
+			except: of = None # Windows
+
+			if of:
+				if of[:5] == 'pipe:':
+					if no_tty:
+						die(2,f'Writing {desc} to pipe is not allowed')
+					if ask_tty and not opt.quiet:
+						confirm_or_raise('',f'output {desc} to pipe')
+						msg('')
+				of2,pd = os.path.relpath(of),os.path.pardir
+				msg('Redirecting output to file {!r}'.format(of if of2[:len(pd)] == pd else of2))
+			else:
+				msg('Redirecting output to file')
+
+		if binary and g.platform == 'win':
+			import msvcrt
+			msvcrt.setmode(sys.stdout.fileno(),os.O_BINARY)
+
+		# MSWin workaround. See msg_r()
+		try:
+			sys.stdout.write(data.decode() if isinstance(data,bytes) else data)
+		except:
+			os.write(1,data if isinstance(data,bytes) else data.encode())
+
+	def do_file(outfile,ask_write_prompt):
+		if opt.outdir and not ignore_opt_outdir and not os.path.isabs(outfile):
+			outfile = make_full_path(opt.outdir,outfile)
+
+		if ask_write:
+			if not ask_write_prompt:
+				ask_write_prompt = f'Save {desc}?'
+			if not keypress_confirm(ask_write_prompt,
+						default_yes=ask_write_default_yes):
+				die(1,f'{capfirst(desc)} not saved')
+
+		hush = False
+		if os.path.lexists(outfile) and ask_overwrite:
+			confirm_or_raise('',f'File {outfile!r} already exists\nOverwrite?')
+			msg(f'Overwriting file {outfile!r}')
+			hush = True
+
+		# not atomic, but better than nothing
+		# if cmp_data is empty, file can be either empty or non-existent
+		if check_data:
+			try:
+				with open(outfile,('r','rb')[bool(binary)]) as fp:
+					d = fp.read()
+			except:
+				d = ''
+			finally:
+				if d != cmp_data:
+					if g.test_suite:
+						print_diff(cmp_data,d)
+					die(3,f'{desc} in file {outfile!r} has been altered by some other program! Aborting file write')
+
+		# To maintain portability, always open files in binary mode
+		# If 'binary' option not set, encode/decode data before writing and after reading
+		try:
+			with _open_or_die(outfile,'wb') as fp:
+				fp.write(data if binary else data.encode())
+		except:
+			die(2,f'Failed to write {desc} to file {outfile!r}')
+
+		if not (hush or quiet):
+			msg(f'{capfirst(desc)} written to file {outfile!r}')
+
+		return True
+
+	if opt.stdout or outfile in ('','-'):
+		do_stdout()
+	elif sys.stdin.isatty() and not sys.stdout.isatty():
+		do_stdout()
+	else:
+		do_file(outfile,ask_write_prompt)
+
+def get_words_from_file(infile,desc,quiet=False):
+
+	if not quiet:
+		qmsg(f'Getting {desc} from file {infile!r}')
+
+	with _open_or_die(infile, 'rb') as fp:
+		data = fp.read()
+
+	try:
+		words = data.decode().split()
+	except:
+		die(1,f'{capfirst(desc)} data must be UTF-8 encoded.')
+
+	dmsg('Sanitized input: [{}]'.format(' '.join(words)))
+
+	return words
+
+def get_data_from_file(infile,desc='data',dash=False,silent=False,binary=False,quiet=False):
+
+	from .opts import opt
+	if not opt.quiet and not silent and not quiet and desc:
+		qmsg(f'Getting {desc} from file {infile!r}')
+
+	with _open_or_die(
+			(0 if dash and infile == '-' else infile),
+			'rb',
+			silent=silent) as fp:
+		data = fp.read(g.max_input_size+1)
+
+	if not binary:
+		data = data.decode()
+
+	if len(data) == g.max_input_size + 1:
+		raise MaxInputSizeExceeded(f'Too much input data!  Max input data size: {f.max_input_size} bytes')
+
+	return data
+
+def _mmgen_decrypt_file_maybe(fn,desc='',quiet=False,silent=False):
+	d = get_data_from_file(fn,desc,binary=True,quiet=quiet,silent=silent)
+	from .crypto import mmenc_ext
+	have_enc_ext = get_extension(fn) == mmenc_ext
+	if have_enc_ext or not is_utf8(d):
+		m = ('Attempting to decrypt','Decrypting')[have_enc_ext]
+		qmsg(f'{m} {desc} {fn!r}')
+		from .crypto import mmgen_decrypt_retry
+		d = mmgen_decrypt_retry(d,desc)
+	return d
+
+def get_lines_from_file(fn,desc='',trim_comments=False,quiet=False,silent=False):
+	dec = _mmgen_decrypt_file_maybe(fn,desc,quiet=quiet,silent=silent)
+	ret = dec.decode().splitlines()
+	if trim_comments:
+		ret = strip_comments(ret)
+	dmsg(f'Got {len(ret)} lines from file {fn!r}')
+	return ret
diff --git a/mmgen/main_addrgen.py b/mmgen/main_addrgen.py
index 7d0cfd32..c2c71cdf 100755
--- a/mmgen/main_addrgen.py
+++ b/mmgen/main_addrgen.py
@@ -145,6 +145,7 @@ if opt.keygen_backend:
 
 idxs = AddrIdxList(fmt_str=cmd_args.pop())
 
+from .fileutil import get_seed_file
 sf = get_seed_file(cmd_args,1)
 
 do_license_msg()
diff --git a/mmgen/main_addrimport.py b/mmgen/main_addrimport.py
index 58b0e992..8ca52b24 100755
--- a/mmgen/main_addrimport.py
+++ b/mmgen/main_addrimport.py
@@ -83,6 +83,7 @@ def parse_cmd_args(rpc,cmd_args):
 
 	if len(cmd_args) == 1:
 		infile = cmd_args[0]
+		from .fileutil import check_infile,get_lines_from_file
 		check_infile(infile)
 		if opt.addrlist:
 			al = AddrList(
diff --git a/mmgen/main_autosign.py b/mmgen/main_autosign.py
index 4394d4ea..514a0fb1 100755
--- a/mmgen/main_autosign.py
+++ b/mmgen/main_autosign.py
@@ -317,6 +317,7 @@ def wipe_existing_key():
 	try: os.stat(fn)
 	except: pass
 	else:
+		from .fileutil import shred_file
 		msg(f'\nShredding existing key {fn!r}')
 		shred_file( fn, verbose=opt.verbose )
 
diff --git a/mmgen/main_passgen.py b/mmgen/main_passgen.py
index 38ed11ca..d6db030f 100755
--- a/mmgen/main_passgen.py
+++ b/mmgen/main_passgen.py
@@ -139,6 +139,7 @@ pw_idxs = AddrIdxList(fmt_str=cmd_args.pop())
 
 pw_id_str = cmd_args.pop()
 
+from .fileutil import get_seed_file
 sf = get_seed_file(cmd_args,1)
 
 pw_fmt = opt.passwd_fmt or PasswordList.dfl_pw_fmt
diff --git a/mmgen/main_seedjoin.py b/mmgen/main_seedjoin.py
index 771c363b..dc02be5b 100755
--- a/mmgen/main_seedjoin.py
+++ b/mmgen/main_seedjoin.py
@@ -118,6 +118,7 @@ if opt.master_share:
 if opt.id_str and not opt.master_share:
 	die(1,'--id-str option meaningless in context of non-master-share join')
 
+from .fileutil import check_infile
 for arg in cmd_args:
 	check_wallet_extension(arg)
 	check_infile(arg)
diff --git a/mmgen/main_txbump.py b/mmgen/main_txbump.py
index dcf92014..5f9d2584 100755
--- a/mmgen/main_txbump.py
+++ b/mmgen/main_txbump.py
@@ -102,6 +102,8 @@ FMT CODES:
 cmd_args = opts.init(opts_data)
 
 tx_file = cmd_args.pop(0)
+
+from .fileutil import check_infile
 check_infile(tx_file)
 
 from .tx import *
diff --git a/mmgen/main_txsend.py b/mmgen/main_txsend.py
index efe16b6d..4089dd50 100755
--- a/mmgen/main_txsend.py
+++ b/mmgen/main_txsend.py
@@ -42,6 +42,7 @@ cmd_args = opts.init(opts_data)
 
 if len(cmd_args) == 1:
 	infile = cmd_args[0]
+	from .fileutil import check_infile
 	check_infile(infile)
 else:
 	opts.usage()
diff --git a/mmgen/main_txsign.py b/mmgen/main_txsign.py
index c0c2a8ac..44718146 100755
--- a/mmgen/main_txsign.py
+++ b/mmgen/main_txsign.py
@@ -100,6 +100,7 @@ infiles = opts.init(opts_data)
 if not infiles:
 	opts.usage()
 
+from .fileutil import check_infile
 for i in infiles:
 	check_infile(i)
 
diff --git a/mmgen/main_wallet.py b/mmgen/main_wallet.py
index 6106897c..b9a457a7 100755
--- a/mmgen/main_wallet.py
+++ b/mmgen/main_wallet.py
@@ -169,6 +169,8 @@ elif invoked_as == 'seedsplit':
 	else:
 		opts.usage()
 
+from .fileutil import check_infile,get_seed_file
+
 if cmd_args:
 	if invoked_as == 'gen' or len(cmd_args) > 1:
 		opts.usage()
@@ -227,6 +229,7 @@ if invoked_as == 'passchg' and ss_in.infile.dirname == g.data_dir:
 	confirm_or_raise(m1,m2,exit_msg='Password not changed')
 	ss_out.write_to_file(desc='New wallet',outdir=g.data_dir)
 	bmsg('Securely deleting old wallet')
+	from .fileutil import shred_file
 	shred_file(
 		ss_in.infile.name,
 		verbose = opt.verbose )
diff --git a/mmgen/opts.py b/mmgen/opts.py
index e2fee23d..9c360f1b 100755
--- a/mmgen/opts.py
+++ b/mmgen/opts.py
@@ -24,6 +24,7 @@ import sys,os,stat
 from .exception import UserOptError
 from .globalvars import g
 from .base_obj import Lockable
+
 import mmgen.share.Opts
 
 class UserOpts(Lockable):
@@ -307,7 +308,7 @@ def init(opts_data=None,add_opts=None,init_opts=None,opt_filter=None,parse_only=
 	else:
 		g.data_dir_root = os.path.join(g.home_dir,'.'+g.proj_name.lower())
 
-	from .util import check_or_create_dir
+	from .fileutil import check_or_create_dir
 	check_or_create_dir(g.data_dir_root)
 
 	from .term import init_term
@@ -516,7 +517,7 @@ def check_usr_opts(usr_opts): # Raises an exception if any check fails
 		fn,offset = a
 		opt_is_int(offset,desc)
 
-		from .util import check_infile,check_outdir,check_outfile
+		from .fileutil import check_infile,check_outdir,check_outfile
 		if key == 'hidden_incog_input_params':
 			check_infile(fn,blkdev_ok=True)
 			key2 = 'in_fmt'
@@ -624,10 +625,10 @@ def check_usr_opts(usr_opts): # Raises an exception if any check fails
 		desc = f'parameter for {fmt_opt(key)!r} option'
 
 		if key in g.infile_opts:
-			from .util import check_infile
+			from .fileutil import check_infile
 			check_infile(val) # file exists and is readable - dies on error
 		elif key == 'outdir':
-			from .util import check_outdir
+			from .fileutil import check_outdir
 			check_outdir(val) # dies on error
 		elif 'chk_'+key in cfuncs:
 			cfuncs['chk_'+key](key,val,desc)
diff --git a/mmgen/rpc.py b/mmgen/rpc.py
index 116b5a6e..34412275 100755
--- a/mmgen/rpc.py
+++ b/mmgen/rpc.py
@@ -23,6 +23,7 @@ rpc.py:  Cryptocoin RPC library for the MMGen suite
 import base64,json,asyncio
 from decimal import Decimal
 from .common import *
+from .fileutil import get_lines_from_file
 from .objmethods import Hilite,InitErrors
 from .base_obj import AsyncInit
 
diff --git a/mmgen/tool.py b/mmgen/tool.py
index 3bb8bf07..dd20bd19 100755
--- a/mmgen/tool.py
+++ b/mmgen/tool.py
@@ -32,6 +32,7 @@ from .passwdlist import PasswordList
 from .baseconv import baseconv
 from .xmrseed import xmrseed
 from .bip39 import bip39
+from .fileutil import get_seed_file,get_data_from_file,write_data_to_file
 
 NL = ('\n','\r\n')[g.platform=='win']
 
diff --git a/mmgen/twctl.py b/mmgen/twctl.py
index 20a23638..55ebf5bd 100755
--- a/mmgen/twctl.py
+++ b/mmgen/twctl.py
@@ -22,15 +22,7 @@ twctl: Tracking wallet control class for the MMGen suite
 
 from .globalvars import g
 from .exception import WalletFileError
-from .util import (
-	msg,
-	dmsg,
-	check_or_create_dir,
-	write_data_to_file,
-	get_data_from_file,
-	write_mode,
-	altcoin_subclass
-)
+from .util import msg,dmsg,write_mode,altcoin_subclass
 from .base_obj import AsyncInit
 from .objmethods import MMGenObject
 from .obj import TwComment,get_obj
@@ -93,6 +85,7 @@ class TrackingWallet(MMGenObject,metaclass=AsyncInit):
 			))
 		self.tw_fn = os.path.join(tw_dir,'tracking-wallet.json')
 
+		from .fileutil import check_or_create_dir,get_data_from_file
 		check_or_create_dir(tw_dir)
 
 		try:
@@ -210,6 +203,7 @@ class TrackingWallet(MMGenObject,metaclass=AsyncInit):
 
 	@write_mode
 	def write_changed(self,data):
+		from .fileutil import write_data_to_file
 		write_data_to_file(
 			self.tw_fn,
 			data,
diff --git a/mmgen/twuo.py b/mmgen/twuo.py
index 60234247..bdd0a5e4 100755
--- a/mmgen/twuo.py
+++ b/mmgen/twuo.py
@@ -35,7 +35,6 @@ from .util import (
 	fmt,
 	make_timestr,
 	keypress_confirm,
-	write_data_to_file,
 	line_input,
 	do_pager,
 	altcoin_subclass
@@ -507,6 +506,7 @@ Actions: [q]uit view, [p]rint to file, pager [v]iew, [w]ide view, add [l]abel:
 					self.proto.dcoin,
 					','.join(self.sort_info(include_group=False)).lower() )
 				msg('')
+				from .fileutil import write_data_to_file
 				try:
 					write_data_to_file(
 						of,
diff --git a/mmgen/tx.py b/mmgen/tx.py
index e5614ba0..432585f2 100755
--- a/mmgen/tx.py
+++ b/mmgen/tx.py
@@ -488,6 +488,7 @@ class MMGenTX:
 		# returns true if comment added or changed
 		def add_comment(self,infile=None):
 			if infile:
+				from .fileutil import get_data_from_file
 				self.label = MMGenTxLabel(get_data_from_file(infile,'transaction comment'))
 			else: # get comment from user, or edit existing comment
 				m = ('Add a comment to transaction?','Edit transaction comment?')[bool(self.label)]
@@ -739,6 +740,7 @@ class MMGenTX:
 			)
 
 			ad_f = AddrData(self.proto)
+			from .fileutil import check_infile
 			for a in addrfiles:
 				check_infile(a)
 				ad_f.add(AddrList(self.proto,a))
diff --git a/mmgen/txfile.py b/mmgen/txfile.py
index 4fea57d9..bbdb6a2b 100755
--- a/mmgen/txfile.py
+++ b/mmgen/txfile.py
@@ -57,6 +57,7 @@ class MMGenTxFile:
 			)[desc=='inputs']
 			return io_list(tx,[io(tx.proto,**e) for e in d])
 
+		from .fileutil import get_data_from_file
 		tx_data = get_data_from_file(infile,tx.desc+' data',quiet=quiet_open)
 
 		try:
@@ -206,6 +207,7 @@ class MMGenTxFile:
 		if not self.fmt_data:
 			self.fmt_data = self.format()
 
+		from .fileutil import write_data_to_file
 		write_data_to_file(
 			outfile               = self.filename,
 			data                  = self.fmt_data,
diff --git a/mmgen/txsign.py b/mmgen/txsign.py
index 8a8f9d20..ab9455d6 100755
--- a/mmgen/txsign.py
+++ b/mmgen/txsign.py
@@ -134,6 +134,7 @@ def get_keyaddrlist(proto,opt):
 
 def get_keylist(proto,opt):
 	if opt.keys_from_file:
+		from .fileutil import get_lines_from_file
 		return get_lines_from_file(opt.keys_from_file,'key-address data',trim_comments=True)
 	return None
 
diff --git a/mmgen/util.py b/mmgen/util.py
index bc796c7f..3852f76e 100755
--- a/mmgen/util.py
+++ b/mmgen/util.py
@@ -20,13 +20,13 @@
 util.py:  Low-level routines imported by other modules in the MMGen suite
 """
 
-import sys,os,time,stat,re
-from subprocess import run,PIPE,DEVNULL
+import sys,os,time,re
 from hashlib import sha256
 from string import hexdigits,digits
+
 from .color import *
-from .exception import *
-from .globalvars import *
+from .exception import BadFileExtension,UserNonConfirmation
+from .globalvars import g
 
 CUR_HIDE = '\033[?25l'
 CUR_SHOW = '\033[?25h'
@@ -239,20 +239,6 @@ def parse_bytespec(nbytes):
 
 	die(1,f'{nbytes!r}: invalid byte specifier')
 
-def check_or_create_dir(path):
-	try:
-		os.listdir(path)
-	except:
-		if os.getenv('MMGEN_TEST_SUITE'):
-			try: # exception handling required for MSWin/MSYS2
-				run(['/bin/rm','-rf',path])
-			except:
-				pass
-		try:
-			os.makedirs(path,0o700)
-		except:
-			die(2,f'ERROR: unable to read or create path {path!r}')
-
 from .opts import opt
 
 def qmsg(s,alt=None):
@@ -460,69 +446,6 @@ def compare_or_die(val1, desc1, val2, desc2, e='Error'):
 	dmsg(f'{capfirst(desc2)} OK ({val2})')
 	return True
 
-def check_binary(args):
-	try:
-		run(args,stdout=DEVNULL,stderr=DEVNULL,check=True)
-	except:
-		rdie(2,f'{args[0]!r} binary missing, not in path, or not executable')
-
-def shred_file(fn,verbose=False):
-	check_binary(['shred','--version'])
-	run(
-		['shred','--force','--iterations=30','--zero','--remove=wipesync']
-		+ (['--verbose'] if verbose else [])
-		+ [fn],
-		check=True )
-
-def open_or_die(filename,mode,silent=False):
-	try:
-		return open(filename,mode)
-	except:
-		die(2,'' if silent else
-			'Unable to open file {!r} for {}'.format(
-				({0:'STDIN',1:'STDOUT',2:'STDERR'}[filename] if type(filename) == int else filename),
-				('reading' if 'r' in mode else 'writing')
-			))
-
-def check_file_type_and_access(fname,ftype,blkdev_ok=False):
-
-	access,op_desc = (
-		(os.W_OK,'writ') if ftype in ('output file','output directory') else
-		(os.R_OK,'read') )
-
-	if ftype == 'output directory':
-		ok_types = [(stat.S_ISDIR, 'output directory')]
-	else:
-		ok_types = [
-			(stat.S_ISREG,'regular file'),
-			(stat.S_ISLNK,'symbolic link')
-		]
-		if blkdev_ok:
-			ok_types.append((stat.S_ISBLK,'block device'))
-
-	try:
-		mode = os.stat(fname).st_mode
-	except:
-		raise FileNotFound(f'Requested {ftype} {fname!r} not found')
-
-	for t in ok_types:
-		if t[0](mode):
-			break
-	else:
-		ok_list = ' or '.join( t[1] for t in ok_types )
-		die(1,f'Requested {ftype} {fname!r} is not a {ok_list}')
-
-	if not os.access(fname,access):
-		die(1,f'Requested {ftype} {fname!r} is not {op_desc}able by you')
-
-	return True
-
-def check_infile(f,blkdev_ok=False):
-	return check_file_type_and_access(f,'input file',blkdev_ok=blkdev_ok)
-def check_outfile(f,blkdev_ok=False):
-	return check_file_type_and_access(f,'output file',blkdev_ok=blkdev_ok)
-def check_outdir(f):
-	return check_file_type_and_access(f,'output directory')
 def check_wallet_extension(fn):
 	from .wallet import Wallet
 	if not Wallet.ext_to_type(get_extension(fn)):
@@ -531,29 +454,6 @@ def check_wallet_extension(fn):
 def make_full_path(outdir,outfile):
 	return os.path.normpath(os.path.join(outdir, os.path.basename(outfile)))
 
-def get_seed_file(cmd_args,nargs,invoked_as=None):
-	from .filename import find_file_in_dir
-	from .wallet import MMGenWallet
-
-	wf = find_file_in_dir(MMGenWallet,g.data_dir)
-
-	wd_from_opt = bool(opt.hidden_incog_input_params or opt.in_fmt) # have wallet data from opt?
-
-	import mmgen.opts as opts
-	if len(cmd_args) + (wd_from_opt or bool(wf)) < nargs:
-		if not wf:
-			msg('No default wallet found, and no other seed source was specified')
-		opts.usage()
-	elif len(cmd_args) > nargs:
-		opts.usage()
-	elif len(cmd_args) == nargs and wf and invoked_as != 'gen':
-		qmsg('Warning: overriding default wallet with user-supplied wallet')
-
-	if cmd_args or wf:
-		check_infile(cmd_args[0] if cmd_args else wf)
-
-	return cmd_args[0] if cmd_args else (wf,None)[wd_from_opt]
-
 def confirm_or_raise(message,q,expect='YES',exit_msg='Exiting at user request'):
 	if message.strip():
 		msg(message.strip())
@@ -562,180 +462,16 @@ def confirm_or_raise(message,q,expect='YES',exit_msg='Exiting at user request'):
 	if line_input(a+b).strip() != expect:
 		raise UserNonConfirmation(exit_msg)
 
-def write_data_to_file( outfile,data,desc='data',
-						ask_write=False,
-						ask_write_prompt='',
-						ask_write_default_yes=True,
-						ask_overwrite=True,
-						ask_tty=True,
-						no_tty=False,
-						quiet=False,
-						binary=False,
-						ignore_opt_outdir=False,
-						check_data=False,
-						cmp_data=None):
-
-	if quiet: ask_tty = ask_overwrite = False
-	if opt.quiet: ask_overwrite = False
-
-	if ask_write_default_yes == False or ask_write_prompt:
-		ask_write = True
-
-	def do_stdout():
-		qmsg('Output to STDOUT requested')
-		if g.stdin_tty:
-			if no_tty:
-				die(2,f'Printing {desc} to screen is not allowed')
-			if (ask_tty and not opt.quiet) or binary:
-				confirm_or_raise('',f'output {desc} to screen')
-		else:
-			try:    of = os.readlink(f'/proc/{os.getpid()}/fd/1') # Linux
-			except: of = None # Windows
-
-			if of:
-				if of[:5] == 'pipe:':
-					if no_tty:
-						die(2,f'Writing {desc} to pipe is not allowed')
-					if ask_tty and not opt.quiet:
-						confirm_or_raise('',f'output {desc} to pipe')
-						msg('')
-				of2,pd = os.path.relpath(of),os.path.pardir
-				msg('Redirecting output to file {!r}'.format(of if of2[:len(pd)] == pd else of2))
-			else:
-				msg('Redirecting output to file')
-
-		if binary and g.platform == 'win':
-			import msvcrt
-			msvcrt.setmode(sys.stdout.fileno(),os.O_BINARY)
-
-		# MSWin workaround. See msg_r()
-		try:
-			sys.stdout.write(data.decode() if isinstance(data,bytes) else data)
-		except:
-			os.write(1,data if isinstance(data,bytes) else data.encode())
-
-	def do_file(outfile,ask_write_prompt):
-		if opt.outdir and not ignore_opt_outdir and not os.path.isabs(outfile):
-			outfile = make_full_path(opt.outdir,outfile)
-
-		if ask_write:
-			if not ask_write_prompt:
-				ask_write_prompt = f'Save {desc}?'
-			if not keypress_confirm(ask_write_prompt,
-						default_yes=ask_write_default_yes):
-				die(1,f'{capfirst(desc)} not saved')
-
-		hush = False
-		if os.path.lexists(outfile) and ask_overwrite:
-			confirm_or_raise('',f'File {outfile!r} already exists\nOverwrite?')
-			msg(f'Overwriting file {outfile!r}')
-			hush = True
-
-		# not atomic, but better than nothing
-		# if cmp_data is empty, file can be either empty or non-existent
-		if check_data:
-			try:
-				with open(outfile,('r','rb')[bool(binary)]) as fp:
-					d = fp.read()
-			except:
-				d = ''
-			finally:
-				if d != cmp_data:
-					if g.test_suite:
-						print_diff(cmp_data,d)
-					die(3,f'{desc} in file {outfile!r} has been altered by some other program! Aborting file write')
-
-		# To maintain portability, always open files in binary mode
-		# If 'binary' option not set, encode/decode data before writing and after reading
-		try:
-			with open_or_die(outfile,'wb') as fp:
-				fp.write(data if binary else data.encode())
-		except:
-			die(2,f'Failed to write {desc} to file {outfile!r}')
-
-		if not (hush or quiet):
-			msg(f'{capfirst(desc)} written to file {outfile!r}')
-
-		return True
-
-	if opt.stdout or outfile in ('','-'):
-		do_stdout()
-	elif sys.stdin.isatty() and not sys.stdout.isatty():
-		do_stdout()
-	else:
-		do_file(outfile,ask_write_prompt)
-
 def get_words_from_user(prompt):
 	words = line_input(prompt, echo=opt.echo_passphrase).split()
 	dmsg('Sanitized input: [{}]'.format(' '.join(words)))
 	return words
 
-def get_words_from_file(infile,desc,quiet=False):
-
-	if not quiet:
-		qmsg(f'Getting {desc} from file {infile!r}')
-
-	with open_or_die(infile, 'rb') as fp:
-		data = fp.read()
-
-	try:
-		words = data.decode().split()
-	except:
-		die(1,f'{capfirst(desc)} data must be UTF-8 encoded.')
-
-	dmsg('Sanitized input: [{}]'.format(' '.join(words)))
-
-	return words
-
-def get_words(infile,desc,prompt):
-	if infile:
-		return get_words_from_file(infile,desc)
-	else:
-		return get_words_from_user(prompt)
-
-def mmgen_decrypt_file_maybe(fn,desc='',quiet=False,silent=False):
-	d = get_data_from_file(fn,desc,binary=True,quiet=quiet,silent=silent)
-	from .crypto import mmenc_ext
-	have_enc_ext = get_extension(fn) == mmenc_ext
-	if have_enc_ext or not is_utf8(d):
-		m = ('Attempting to decrypt','Decrypting')[have_enc_ext]
-		qmsg(f'{m} {desc} {fn!r}')
-		from .crypto import mmgen_decrypt_retry
-		d = mmgen_decrypt_retry(d,desc)
-	return d
-
-def get_lines_from_file(fn,desc='',trim_comments=False,quiet=False,silent=False):
-	dec = mmgen_decrypt_file_maybe(fn,desc,quiet=quiet,silent=silent)
-	ret = dec.decode().splitlines()
-	if trim_comments:
-		ret = strip_comments(ret)
-	dmsg(f'Got {len(ret)} lines from file {fn!r}')
-	return ret
-
 def get_data_from_user(desc='data'): # user input MUST be UTF-8
 	data = line_input(f'Enter {desc}: ',echo=opt.echo_passphrase)
 	dmsg(f'User input: [{data}]')
 	return data
 
-def get_data_from_file(infile,desc='data',dash=False,silent=False,binary=False,quiet=False):
-
-	if not opt.quiet and not silent and not quiet and desc:
-		qmsg(f'Getting {desc} from file {infile!r}')
-
-	with open_or_die(
-			(0 if dash and infile == '-' else infile),
-			'rb',
-			silent=silent) as fp:
-		data = fp.read(g.max_input_size+1)
-
-	if not binary:
-		data = data.decode()
-
-	if len(data) == g.max_input_size + 1:
-		raise MaxInputSizeExceeded(f'Too much input data!  Max input data size: {f.max_input_size} bytes')
-
-	return data
-
 class oneshot_warning:
 
 	color = 'nocolor'
@@ -860,6 +596,7 @@ def do_pager(text):
 	if 'PAGER' in os.environ and os.environ['PAGER'] != pagers[0]:
 		pagers = [os.environ['PAGER']] + pagers
 
+	from subprocess import run
 	for pager in pagers:
 		try:
 			m = text + ('' if pager == 'less' else end_msg)
diff --git a/mmgen/wallet.py b/mmgen/wallet.py
index 1e90adfe..cc248e7f 100755
--- a/mmgen/wallet.py
+++ b/mmgen/wallet.py
@@ -162,6 +162,7 @@ class Wallet(MMGenObject,metaclass=WalletMeta):
 
 	def _get_data(self):
 		if hasattr(self,'infile'):
+			from .fileutil import get_data_from_file
 			self.fmt_data = get_data_from_file(self.infile.name,self.desc,binary=self.file_mode=='binary')
 		elif self.in_data:
 			self.fmt_data = self.in_data
@@ -238,6 +239,7 @@ class Wallet(MMGenObject,metaclass=WalletMeta):
 		# write_data_to_file(): outfile with absolute path overrides opt.outdir
 		if outdir:
 			of = os.path.abspath(os.path.join(outdir,self._filename()))
+		from .fileutil import write_data_to_file
 		write_data_to_file(of if outdir else self._filename(),self.fmt_data,**kwargs)
 
 class WalletUnenc(Wallet):
@@ -332,6 +334,7 @@ class WalletEnc(Wallet):
 				self.desc
 			)
 		if self.passwd_file:
+			from .fileutil import get_words_from_file
 			pw = ' '.join(get_words_from_file(
 				self.passwd_file,
 				desc,
@@ -365,6 +368,7 @@ class WalletEnc(Wallet):
 			('',' '+add_desc)[bool(add_desc)]
 		)
 		if self.passwd_file:
+			from .fileutil import get_words_from_file
 			ret = ' '.join(get_words_from_file(
 				self.passwd_file,
 				desc,
diff --git a/mmgen/xmrwallet.py b/mmgen/xmrwallet.py
index 0c07e301..24fdf79e 100755
--- a/mmgen/xmrwallet.py
+++ b/mmgen/xmrwallet.py
@@ -163,6 +163,7 @@ class MoneroMMGenTX:
 				self.data.amount,
 				(lambda s: '' if s == 'mainnet' else f'.{s}')(self.data.network),
 			)
+			from .fileutil import write_data_to_file
 			write_data_to_file(fn,out,desc='MoneroMMGenTX data',ask_write=True,ask_write_default_yes=False)
 
 	class NewSigned(Base):
@@ -191,6 +192,7 @@ class MoneroMMGenTX:
 	class Signed(Base):
 
 		def __init__(self,fn):
+			from .fileutil import get_data_from_file
 			self.fn = fn
 			d_wrap = json.loads(get_data_from_file(fn))['MoneroMMGenTX']
 			d = self.xmrwallet_tx_data(**d_wrap['data'])
diff --git a/scripts/compute-file-chksum.py b/scripts/compute-file-chksum.py
index f21fafb0..4971fa09 100755
--- a/scripts/compute-file-chksum.py
+++ b/scripts/compute-file-chksum.py
@@ -19,6 +19,7 @@ opts_data = {
 
 cmd_args = opts.init(opts_data)
 
+from mmgen.fileutil import get_lines_from_file
 lines = get_lines_from_file(cmd_args[0])
 start = (1,0)[bool(opt.include_first_line)]
 a = make_chksum_6(' '.join(lines[start:]).encode())
diff --git a/test/include/common.py b/test/include/common.py
index 17348729..e3ece6cc 100755
--- a/test/include/common.py
+++ b/test/include/common.py
@@ -26,6 +26,7 @@ class TestSuiteFatalException(Exception): pass
 import os
 from mmgen.common import *
 from mmgen.devtools import *
+from mmgen.fileutil import write_data_to_file,get_data_from_file
 
 def strip_ansi_escapes(s):
 	import re
@@ -130,7 +131,6 @@ def write_to_tmpfile(cfg,fn,data,binary=False):
 	write_to_file(  os.path.join(cfg['tmpdir'],fn), data=data, binary=binary )
 
 def read_from_file(fn,binary=False):
-	from mmgen.util import get_data_from_file
 	return get_data_from_file(fn,quiet=True,binary=binary)
 
 def read_from_tmpfile(cfg,fn,binary=False):
diff --git a/test/overlay/fakemods/twuo.py b/test/overlay/fakemods/twuo.py
index 42204387..86b4d9d5 100644
--- a/test/overlay/fakemods/twuo.py
+++ b/test/overlay/fakemods/twuo.py
@@ -10,7 +10,7 @@ if os.getenv('MMGEN_BOGUS_WALLET_DATA'):
 	async def fake_get_unspent_rpc(foo):
 		from decimal import Decimal
 		import json
-		from mmgen.util import get_data_from_file
+		from mmgen.fileutil import get_data_from_file
 		return json.loads(get_data_from_file(os.getenv('MMGEN_BOGUS_WALLET_DATA')),parse_float=Decimal)
 
 	TwUnspentOutputs.set_dates = fake_set_dates
diff --git a/test/test_py_d/ts_main.py b/test/test_py_d/ts_main.py
index 67cf0bff..561b3d6f 100755
--- a/test/test_py_d/ts_main.py
+++ b/test/test_py_d/ts_main.py
@@ -22,6 +22,7 @@ ts_main.py: Basic operations tests for the test.py test suite
 
 from mmgen.globalvars import g
 from mmgen.opts import opt
+from mmgen.fileutil import get_data_from_file,write_data_to_file
 from mmgen.wallet import Wallet,MMGenWallet,MMGenMnemonic,IncogWallet,MMGenSeedFile
 from mmgen.rpc import rpc_init
 from ..include.common import *
diff --git a/test/test_py_d/ts_regtest.py b/test/test_py_d/ts_regtest.py
index 8e7249c9..aed9e093 100755
--- a/test/test_py_d/ts_regtest.py
+++ b/test/test_py_d/ts_regtest.py
@@ -24,7 +24,7 @@ import os,json
 from decimal import Decimal
 from mmgen.globalvars import g
 from mmgen.opts import opt
-from mmgen.util import die,gmsg,write_data_to_file
+from mmgen.util import die,gmsg
 from mmgen.protocol import init_proto
 from mmgen.addrlist import AddrList
 from mmgen.wallet import MMGenWallet
@@ -293,6 +293,7 @@ class TestSuiteRegtest(TestSuiteBase,TestSuiteShared):
 				if n % 2: a.set_comment(idx,f'Test address {n}')
 		af = a.get_file()
 		af.format(add_comments=True)
+		from mmgen.fileutil import write_data_to_file
 		write_data_to_file(outfile,af.fmt_data,quiet=True,ignore_opt_outdir=True)
 		end_silence()