diff --git a/cmds/mmgen-seedjoin b/cmds/mmgen-seedjoin
new file mode 100755
index 00000000..8870dd2c
--- /dev/null
+++ b/cmds/mmgen-seedjoin
@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+
+# mmgen = Multi-Mode GENerator, command-line Bitcoin cold storage solution
+# Copyright (C)2013-2019 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/>.
+
+"""
+mmgen-seedjoin: Recreate an MMGen deterministic wallet from its component shares
+"""
+
+from mmgen.main import launch
+launch("seedjoin")
diff --git a/cmds/mmgen-seedsplit b/cmds/mmgen-seedsplit
new file mode 100755
index 00000000..7b27c037
--- /dev/null
+++ b/cmds/mmgen-seedsplit
@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+
+# mmgen = Multi-Mode GENerator, command-line Bitcoin cold storage solution
+# Copyright (C)2013-2019 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/>.
+
+"""
+mmgen-seedsplit: Generate a seed split from an MMGen deterministic wallet
+"""
+
+from mmgen.main import launch
+launch("seedsplit")
diff --git a/mmgen/common.py b/mmgen/common.py
index 3b9b7e73..4bccc607 100755
--- a/mmgen/common.py
+++ b/mmgen/common.py
@@ -28,7 +28,7 @@ from mmgen.opts import opt
 from mmgen.util import *
 
 def help_notes(k):
-	from mmgen.obj import SubSeedIdxRange
+	from mmgen.obj import SubSeedIdxRange,SeedShareIdx,SeedShareCount,MasterShareIdx
 	from mmgen.seed import SeedSource
 	from mmgen.tx import MMGenTX
 	def fee_spec_letters(use_quotes=False):
@@ -41,6 +41,77 @@ def help_notes(k):
 	return {
 		'rel_fee_desc': MMGenTX().rel_fee_desc,
 		'fee_spec_letters': fee_spec_letters(),
+		'seedsplit': """
+COMMAND NOTES:
+
+This command generates shares one at a time.  Shares may be output to any
+MMGen wallet format, with one limitation: only one share in a given split may
+be in hidden incognito format, and it must be the master share in the case of
+a master-share split.
+
+If the command's optional first argument is omitted, the default wallet is
+used for the split.
+
+The last argument is a seed split specifier consisting of an optional split
+ID, a share index, and a share count, all separated by colons.  The split ID
+must be a valid UTF-8 string.  If omitted, the ID 'default' is used.  The
+share index (the index of the share being generated) must be in the range
+{sia}-{sib} and the share count (the total number of shares in the split)
+in the range {sca}-{scb}.
+
+Master Shares
+
+Each seed has a total of {msb} master shares, which can be used as the first
+shares in multiple splits if desired.  To generate a master share, use the
+--master-share (-M) option with an index in the range {msa}-{msb} and omit
+the last argument.
+
+When creating and joining a split using a master share, ensure that the same
+master share index is used in all split and join commands.
+
+EXAMPLES:
+
+  Create a 3-way default split of your default wallet, outputting all shares
+  to default wallet format.  Rejoin the split:
+
+    $ mmgen-seedsplit 1:3 # Step A
+    $ mmgen-seedsplit 2:3 # Step B
+    $ mmgen-seedsplit 3:3 # Step C
+    $ mmgen-seedjoin <output_of_step_A> <output_of_step_B> <output_of_step_C>
+
+  Create a 2-way split of your default wallet with ID string 'alice',
+  outputting shares to MMGen native mnemonic format.  Rejoin the split:
+
+    $ mmgen-seedsplit -o words alice:1:2 # Step D
+    $ mmgen-seedsplit -o words alice:2:2 # Step E
+    $ mmgen-seedjoin <output_of_step_D> <output_of_step_E>
+
+  Create a 2-way split of your default wallet with ID string 'bob' using
+  master share #7, outputting share #1 (the master share) to default wallet
+  format and share #2 to BIP39 format.  Rejoin the split:
+
+    $ mmgen-seedsplit -M7                   # Step X
+    $ mmgen-seedsplit -M7 -o bip39 bob:2:2  # Step Y
+    $ mmgen-seedjoin -M7 --id-str=bob <output_of_step_X> <output_of_step_Y>
+
+  Create a 2-way split of your default wallet with ID string 'alice' using
+  master share #7.  Rejoin the split using master share #7 generated in the
+  previous example:
+
+    $ mmgen-seedsplit -M7 -o bip39 alice:2:2 # Step Z
+    $ mmgen-seedjoin -M7 --id-str=alice <output_of_step_X> <output_of_step_Z>
+
+  Create a 2-way default split of your default wallet with an incognito-format
+  master share hidden in file 'my.hincog' at offset 1325.  Rejoin the split:
+
+    $ mmgen-seedsplit -M4 -o hincog -J my.hincog,1325 1:2 # Step M (share A)
+    $ mmgen-seedsplit -M4 -o bip39 2:2                    # Step N (share B)
+    $ mmgen-seedjoin -M4 -H my.hincog,1325 <output_of_step_N>
+
+""".strip().format(
+	sia=SeedShareIdx.min_val,sib=SeedShareIdx.max_val,
+	sca=SeedShareCount.min_val,scb=SeedShareCount.max_val,
+	msa=MasterShareIdx.min_val,msb=MasterShareIdx.max_val),
 		'subwallet': """
 SUBWALLETS:
 
diff --git a/mmgen/main.py b/mmgen/main.py
index a791717f..45549de9 100755
--- a/mmgen/main.py
+++ b/mmgen/main.py
@@ -22,7 +22,7 @@ main.py - Script launcher for the MMGen suite
 
 def launch(mod):
 
-	if mod in ('walletgen','walletchk','walletconv','passchg','subwalletgen'):
+	if mod in ('walletgen','walletchk','walletconv','passchg','subwalletgen','seedsplit'):
 		mod = 'wallet'
 	if mod == 'keygen': mod = 'addrgen'
 
diff --git a/mmgen/main_seedjoin.py b/mmgen/main_seedjoin.py
new file mode 100755
index 00000000..45dbedcf
--- /dev/null
+++ b/mmgen/main_seedjoin.py
@@ -0,0 +1,146 @@
+#!/usr/bin/env python3
+#
+# mmgen = Multi-Mode GENerator, command-line Bitcoin cold storage solution
+# Copyright (C)2013-2019 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/>.
+
+"""
+mmgen/main_seedjoin: Regenerate an MMGen deterministic wallet from seed shares
+                     created by 'mmgen-seedsplit'
+"""
+
+from mmgen.common import *
+from mmgen.obj import MasterShareIdx,SeedSplitIDString,MMGenWalletLabel
+from mmgen.seed import Seed,SeedSource,SeedShareMasterJoining
+
+opts_data = {
+	'text': {
+		'desc': """Regenerate an MMGen deterministic wallet from seed shares
+                  created by 'mmgen-seedsplit'""",
+		'usage': '[options] share1 share2 [...shareN]',
+		'options': """
+-h, --help            Print this help message
+--, --longhelp        Print help message for long options (common options)
+-d, --outdir=      d  Output file to directory 'd' instead of working dir
+-e, --echo-passphrase Echo passphrases and other user input to screen
+-i, --id-str=      s  ID String of split (required for master share join only)
+-H, --hidden-incog-input-params=f,o  Read hidden incognito data from file
+                      'f' at offset 'o' (comma-separated).  NOTE: only the
+                      first share may be in hidden incognito format!
+-J, --hidden-incog-output-params=f,o  Write hidden incognito data to file
+                      'f' at offset 'o' (comma-separated). File 'f' will be
+                      created if necessary and filled with random data.
+-o, --out-fmt=     f  Output to wallet format 'f' (see FMT CODES below)
+-O, --old-incog-fmt   Specify old-format incognito input
+-L, --label=       l  Specify a label 'l' for output wallet
+-M, --master-share=i  Use a master share with index 'i' (min:{ms_min}, max:{ms_max})
+-p, --hash-preset= p  Use the scrypt hash parameters defined by preset 'p'
+                      for password hashing (default: '{g.hash_preset}')
+-z, --show-hash-presets Show information on available hash presets
+-P, --passwd-file= f  Get wallet passphrase from file 'f'
+-q, --quiet           Produce quieter output; suppress some warnings
+-r, --usr-randchars=n Get 'n' characters of additional randomness from user
+                      (min={g.min_urandchars}, max={g.max_urandchars}, default={g.usr_randchars})
+-S, --stdout          Write wallet data to stdout instead of file
+-v, --verbose         Produce more verbose output
+""",
+	'notes': """
+
+COMMAND NOTES:
+
+When joining with a master share, the master share must be listed first.
+The remaining shares may be listed in any order.
+
+The --id-str option is required only for master share joins.  For ordinary
+joins it will be ignored.
+
+For usage examples, see the help screen for the 'mmgen-seedsplit' command.
+
+{n_pw}
+
+FMT CODES:
+
+  {f}
+"""
+	},
+	'code': {
+		'options': lambda s: s.format(
+			ms_min=MasterShareIdx.min_val,
+			ms_max=MasterShareIdx.max_val,
+			g=g,
+		),
+		'notes': lambda s: s.format(
+			f='\n  '.join(SeedSource.format_fmt_codes().splitlines()),
+			n_pw=help_notes('passwd'),
+		)
+	}
+}
+
+def print_shares_info():
+	si,out = 0,'\nComputed shares:\n'
+	if opt.master_share:
+		fs = '{:3}: {}->{} ' + yellow('(master share #{}, split id ') + '{}' + yellow(', share count {})\n')
+		out += fs.format(
+				1,
+				shares[0].sid,
+				share1.sid,
+				master_idx,
+				id_str.hl(encl="''"),
+				len(shares) )
+		si = 1
+	for n,s in enumerate(shares[si:],si+1):
+		out += '{:3}: {}\n'.format(n,s.sid)
+	qmsg(out)
+
+cmd_args = opts.init(opts_data)
+
+if len(cmd_args) + bool(opt.hidden_incog_input_params) < 2:
+	opts.usage()
+
+if opt.label:
+	opt.label = MMGenWalletLabel(opt.label,msg="Error in option '--label'")
+
+if opt.master_share:
+	master_idx = MasterShareIdx(opt.master_share)
+	id_str = SeedSplitIDString(opt.id_str or 'default')
+
+if opt.id_str and not opt.master_share:
+	die(1,'--id-str option meaningless in context of non-master-share join')
+
+for arg in cmd_args:
+	check_wallet_extension(arg)
+	check_infile(arg)
+
+do_license_msg()
+
+qmsg('Input files:\n  {}\n'.format('\n  '.join(cmd_args)))
+
+shares = [SeedSource().seed] if opt.hidden_incog_input_params else []
+shares += [SeedSource(fn).seed for fn in cmd_args]
+
+if opt.master_share:
+	share1 = SeedShareMasterJoining(master_idx,shares[0],id_str,len(shares)).derived_seed
+else:
+	share1 = shares[0]
+
+print_shares_info()
+
+msg_r('Joining {n}-of-{n} XOR split...'.format(n=len(shares)))
+
+seed_out = Seed.join_shares([share1]+shares[1:])
+
+msg('OK\nJoined Seed ID: {}'.format(seed_out.sid.hl()))
+
+SeedSource(seed=seed_out).write_to_file()
diff --git a/mmgen/main_wallet.py b/mmgen/main_wallet.py
index bf9fa98a..b7b5027a 100755
--- a/mmgen/main_wallet.py
+++ b/mmgen/main_wallet.py
@@ -24,7 +24,7 @@ import os
 from mmgen.common import *
 from mmgen.seed import SeedSource,Wallet
 from mmgen.filename import find_file_in_dir
-from mmgen.obj import MMGenWalletLabel
+from mmgen.obj import MMGenWalletLabel,MasterShareIdx
 
 usage = '[opts] [infile]'
 nargs = 1
@@ -32,6 +32,7 @@ iaction = 'convert'
 oaction = 'convert'
 do_bw_note = True
 do_sw_note = False
+do_ss_note = False
 
 invoked_as = {
 	'mmgen-walletgen':    'gen',
@@ -39,6 +40,7 @@ invoked_as = {
 	'mmgen-walletchk':    'chk',
 	'mmgen-passchg':      'passchg',
 	'mmgen-subwalletgen': 'subgen',
+	'mmgen-seedsplit':    'seedsplit',
 }[g.prog_name]
 
 dsw = 'the default or specified {pnm} wallet'
@@ -69,6 +71,13 @@ elif invoked_as == 'subgen':
 	iaction = 'input'
 	oaction = 'output'
 	do_sw_note = True
+elif invoked_as == 'seedsplit':
+	desc = 'Generate a seed share from ' + dsw
+	opt_filter = 'dehHiJlLMIoOpPqrSvz-'
+	usage = '[opts] [infile] [<Split ID String>:]<index>:<share count>'
+	iaction = 'input'
+	oaction = 'output'
+	do_ss_note = True
 
 opts_data = {
 	'text': {
@@ -95,6 +104,7 @@ opts_data = {
                       with non-standard (< {g.seed_len}-bit) seed lengths.
 -L, --label=       l  Specify a label 'l' for output wallet
 -m, --keep-label      Reuse label of input wallet for output wallet
+-M, --master-share=i  Use a master share with index 'i' (min:{ms_min}, max:{ms_max})
 -p, --hash-preset= p  Use the scrypt hash parameters defined by preset 'p'
                       for password hashing (default: '{g.hash_preset}')
 -z, --show-hash-presets Show information on available hash presets
@@ -107,7 +117,7 @@ opts_data = {
 """,
 	'notes': """
 
-{n_sw}{n_pw}{n_bw}
+{n_ss}{n_sw}{n_pw}{n_bw}
 
 FMT CODES:
 
@@ -118,10 +128,13 @@ FMT CODES:
 		'options': lambda s: s.format(
 			iaction=capfirst(iaction),
 			oaction=capfirst(oaction),
+			ms_min=MasterShareIdx.min_val,
+			ms_max=MasterShareIdx.max_val,
 			g=g,
 		),
 		'notes': lambda s: s.format(
 			f='\n  '.join(SeedSource.format_fmt_codes().splitlines()),
+			n_ss=('',help_notes('seedsplit')+'\n\n')[do_ss_note],
 			n_sw=('',help_notes('subwallet')+'\n\n')[do_sw_note],
 			n_pw=help_notes('passwd'),
 			n_bw=('','\n\n'+help_notes('brainwallet'))[do_bw_note]
@@ -137,6 +150,24 @@ if opt.label:
 if invoked_as == 'subgen':
 	from mmgen.obj import SubSeedIdx
 	ss_idx = SubSeedIdx(cmd_args.pop())
+elif invoked_as == 'seedsplit':
+	from mmgen.obj import SeedSplitSpecifier
+	master_share = MasterShareIdx(opt.master_share) if opt.master_share else None
+	if cmd_args:
+		sss = SeedSplitSpecifier(cmd_args.pop(),on_fail='silent')
+		if master_share:
+			if not sss:
+				sss = SeedSplitSpecifier('1:2')
+			elif sss.idx == 1:
+				m1 = 'Share index of 1 meaningless in master share context.'
+				m2 = 'To generate a master share, omit the seed split specifier.'
+				die(1,m1+'  '+m2)
+		elif not sss:
+			opts.usage()
+	elif master_share:
+		sss = SeedSplitSpecifier('1:2')
+	else:
+		opts.usage()
 
 if cmd_args:
 	if invoked_as == 'gen' or len(cmd_args) > 1:
@@ -164,10 +195,15 @@ if invoked_as == 'chk':
 	sys.exit(0)
 
 if invoked_as != 'gen':
-	gmsg('Processing output wallet')
+	gmsg_r('Processing output wallet' + ('\n',' ')[invoked_as == 'seedsplit'])
 
 if invoked_as == 'subgen':
 	ss_out = SeedSource(seed_bin=ss_in.seed.subseed(ss_idx,print_msg=True).data)
+elif invoked_as == 'seedsplit':
+	shares = ss_in.seed.split(sss.count,sss.id,master_share)
+	seed_out = shares.get_share_by_idx(sss.idx,base_seed=True)
+	msg(seed_out.get_desc(ui=True))
+	ss_out = SeedSource(seed=seed_out)
 else:
 	ss_out = SeedSource(ss=ss_in,passchg=invoked_as=='passchg')
 
diff --git a/mmgen/obj.py b/mmgen/obj.py
index 0112938f..305d4cd9 100755
--- a/mmgen/obj.py
+++ b/mmgen/obj.py
@@ -39,6 +39,7 @@ def is_addrlist_id(s):   return AddrListID(s,on_fail='silent')
 def is_tw_label(s):      return TwLabel(s,on_fail='silent')
 def is_wif(s):           return WifKey(s,on_fail='silent')
 def is_viewkey(s):       return ViewKey(s,on_fail='silent')
+def is_seed_split_specifier(s): return SeedSplitSpecifier(s,on_fail='silent')
 
 def truncate_str(s,width): # width = screen width
 	wide_count = 0
@@ -822,6 +823,23 @@ class MMGenPWIDString(MMGenLabel):
 	forbidden = list(' :/\\')
 	trunc_ok = False
 
+class SeedSplitSpecifier(str,Hilite,InitErrors,MMGenObject):
+	color = 'red'
+	def __new__(cls,s,on_fail='raise'):
+		if type(s) == cls: return s
+		cls.arg_chk(on_fail)
+		try:
+			arr = s.split(':')
+			assert len(arr) in (2,3), 'cannot be parsed'
+			a,b,c = arr if len(arr) == 3 else ['default'] + arr
+			me = str.__new__(cls,s)
+			me.id = SeedSplitIDString(a,on_fail=on_fail)
+			me.idx = SeedShareIdx(b,on_fail=on_fail)
+			me.count = SeedShareCount(c,on_fail=on_fail)
+			assert me.idx <= me.count, 'share index greater than share count'
+			return me
+		except Exception as e:
+			return cls.init_fail(e,s)
 
 class SeedSplitIDString(MMGenPWIDString):
 	desc = 'seed split ID string'
diff --git a/mmgen/seed.py b/mmgen/seed.py
index c4786609..a40f7336 100755
--- a/mmgen/seed.py
+++ b/mmgen/seed.py
@@ -366,7 +366,38 @@ class SeedShareList(SubSeedList):
 
 		return hdr + body1 + ''.join(body)
 
-class SeedShare(SubSeed):
+class SeedShareBase(MMGenObject):
+
+	@property
+	def fn_stem(self):
+		pl = self.parent_list
+		msdata = '_with_master{}'.format(pl.master_share.idx) if pl.master_share else ''
+		return '{}-{}-{}of{}{}[{}]'.format(
+			pl.parent_seed.sid,
+			pl.id_str,
+			self.idx,
+			pl.count,
+			msdata,
+			self.sid)
+
+	@property
+	def desc(self):
+		return self.get_desc()
+
+	def get_desc(self,ui=False):
+		pl = self.parent_list
+		mss = ', with master share #{}'.format(pl.master_share.idx) if pl.master_share else ''
+		if ui:
+			m   = ( yellow("(share {} of {} of ")
+					+ pl.parent_seed.sid.hl()
+					+ yellow(', split id ')
+					+ pl.id_str.hl(encl="''")
+					+ yellow('{})') )
+		else:
+			m = "share {} of {} of " + pl.parent_seed.sid + ", split id '" + pl.id_str + "'{}"
+		return m.format(self.idx,pl.count,mss)
+
+class SeedShare(SeedShareBase,SubSeed):
 
 	@staticmethod
 	def make_subseed_bin(parent_list,idx:int,nonce:int,length:str):
@@ -380,7 +411,7 @@ class SeedShare(SubSeed):
 			scramble_key += b':master:' + parent_list.master_share.idx.to_bytes(2,'big')
 		return scramble_seed(seed.data,scramble_key)[:seed.byte_len]
 
-class SeedShareLast(SeedBase):
+class SeedShareLast(SeedShareBase,SeedBase):
 
 	idx = MMGenImmutableAttr('idx',SeedShareIdx)
 	nonce = 0
@@ -401,7 +432,7 @@ class SeedShareLast(SeedBase):
 
 		return ret.to_bytes(seed.byte_len,'big')
 
-class SeedShareMaster(SeedBase):
+class SeedShareMaster(SeedBase,SeedShareBase):
 
 	idx = MMGenImmutableAttr('idx',MasterShareIdx)
 	nonce = MMGenImmutableAttr('nonce',int,typeconv=False)
@@ -414,6 +445,13 @@ class SeedShareMaster(SeedBase):
 
 		self.derived_seed = SeedBase(self.make_derived_seed_bin(parent_list.id_str,parent_list.count))
 
+	@property
+	def fn_stem(self):
+		return '{}-MASTER{}[{}]'.format(
+			self.parent_list.parent_seed.sid,
+			self.idx,
+			self.sid)
+
 	def make_base_seed_bin(self):
 		seed = self.parent_list.parent_seed
 		# field maximums: idx: 65535 (1024)
@@ -427,6 +465,11 @@ class SeedShareMaster(SeedBase):
 		scramble_key = id_str.encode() + b':' + count.to_bytes(2,'big')
 		return scramble_seed(self.data,scramble_key)[:self.byte_len]
 
+	def get_desc(self,ui=False):
+		psid = self.parent_list.parent_seed.sid
+		mss = 'master share #{} of '.format(self.idx)
+		return yellow('(' + mss) + psid.hl() + yellow(')') if ui else mss + psid
+
 class SeedShareMasterJoining(SeedShareMaster):
 
 	id_str = MMGenImmutableAttr('id_str',SeedSplitIDString)
diff --git a/mmgen/tool.py b/mmgen/tool.py
index 0cf1748f..c5bffe17 100755
--- a/mmgen/tool.py
+++ b/mmgen/tool.py
@@ -726,6 +726,17 @@ class MMGenToolCmdWallet(MMGenToolCmdBase):
 		from mmgen.seed import SeedSource
 		return SeedSource(sf).seed.subseeds.format(*SubSeedIdxRange(subseed_idx_range))
 
+	def list_shares(self,
+			share_count:int,
+			id_str='default',
+			master_share:"(min:1, max:{}, 0=no master share)".format(MasterShareIdx.max_val)=0,
+			wallet=''):
+		"list the Seed IDs of the shares resulting from a split of default or specified wallet"
+		opt.quiet = True
+		sf = get_seed_file([wallet] if wallet else [],1)
+		from mmgen.seed import SeedSource
+		return SeedSource(sf).seed.split(share_count,id_str,master_share).format()
+
 	def gen_key(self,mmgen_addr:str,wallet=''):
 		"generate a single MMGen WIF key from default or specified wallet"
 		return self.gen_addr(mmgen_addr,wallet,target='wif')
diff --git a/setup.py b/setup.py
index acff062b..a19c961b 100755
--- a/setup.py
+++ b/setup.py
@@ -142,6 +142,7 @@ setup(
 			'mmgen.main_autosign',
 			'mmgen.main_passgen',
 			'mmgen.main_regtest',
+			'mmgen.main_seedjoin',
 			'mmgen.main_split',
 			'mmgen.main_tool',
 			'mmgen.main_txbump',
@@ -166,6 +167,8 @@ setup(
 			'cmds/mmgen-walletchk',
 			'cmds/mmgen-walletconv',
 			'cmds/mmgen-walletgen',
+			'cmds/mmgen-seedsplit',
+			'cmds/mmgen-seedjoin',
 			'cmds/mmgen-split',
 			'cmds/mmgen-txcreate',
 			'cmds/mmgen-txbump',
diff --git a/test/objtest_py_d/ot_btc_mainnet.py b/test/objtest_py_d/ot_btc_mainnet.py
index a5b9e14c..bb7da71e 100755
--- a/test/objtest_py_d/ot_btc_mainnet.py
+++ b/test/objtest_py_d/ot_btc_mainnet.py
@@ -13,6 +13,8 @@ from mmgen.obj import *
 from mmgen.seed import *
 from .ot_common import *
 
+ssm = str(SeedShareCount.max_val)
+
 tests = OrderedDict([
 	('AddrIdx', {
 		'bad':  ('s',1.1,10000000,-1,0),
@@ -202,4 +204,10 @@ tests = OrderedDict([
 			{'s':'P','ret':'P'},
 		)
 	}),
+	('SeedSplitSpecifier', {
+		'bad': ('M','αβ:2',1,'0:1','1:1','2:1','3:2','1:2000','abc:0:2'),
+		'good': (
+			('1:2','2:2','alice:2:2','αβ:2:2','1:'+ssm,ssm+':'+ssm)
+		)
+	}),
 ])
diff --git a/test/test.py b/test/test.py
index 888a7c7e..76c78f5a 100755
--- a/test/test.py
+++ b/test/test.py
@@ -322,6 +322,7 @@ cfgs = { # addr_idx_lists (except 31,32,33,34) must contain exactly 8 addresses
 		},
 	},
 	'22': {},
+	'23': {},
 	'31': {},
 	'32': {},
 	'33': {},
@@ -448,6 +449,7 @@ class CmdGroupMgr(object):
 		'ref3':             ('TestSuiteRef3Seed',{'is3seed':True,'modname':'ref_3seed'}),
 		'ref':              ('TestSuiteRef',{}),
 		'ref_altcoin':      ('TestSuiteRefAltcoin',{}),
+		'seedsplit':        ('TestSuiteSeedSplit',{}),
 		'tool':             ('TestSuiteTool',{'modname':'misc','full_data':True}),
 		'input':            ('TestSuiteInput',{'modname':'misc','full_data':True}),
 		'output':           ('TestSuiteOutput',{'modname':'misc','full_data':True}),
diff --git a/test/test_py_d/ts_seedsplit.py b/test/test_py_d/ts_seedsplit.py
new file mode 100755
index 00000000..6fe75fd9
--- /dev/null
+++ b/test/test_py_d/ts_seedsplit.py
@@ -0,0 +1,248 @@
+#!/usr/bin/env python3
+#
+# mmgen = Multi-Mode GENerator, command-line Bitcoin cold storage solution
+# Copyright (C)2013-2019 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/>.
+
+"""
+ts_seedsplit.py: Seed split/join tests for the test.py test suite
+"""
+
+from mmgen.globalvars import g
+from mmgen.opts import opt
+
+from test.test_py_d.ts_base import *
+
+ref_wf = 'test/ref/98831F3A.bip39'
+ref_sid = '98831F3A'
+wpasswd = 'abc'
+sh1_passwd = 'xyz'
+
+class TestSuiteSeedSplit(TestSuiteBase):
+	'splitting and joining seeds'
+	networks = ('btc',)
+	tmpdir_nums = [23]
+	cmd_group = (
+		('ss_walletgen',                'wallet generation'),
+		('ss_2way_A_dfl1',              '2-way seed split (share A)'),
+		('ss_2way_B_dfl1',              '2-way seed split (share B)'),
+		('ss_2way_join_dfl1',           '2-way seed join'),
+		('ss_2way_A_dfl2',              "2-way seed split 'default' (share A)"),
+		('ss_2way_B_dfl2',              "2-way seed split 'default' (share B)"),
+		('ss_2way_join_dfl2',           "2-way seed join 'default'"),
+		('ss_2way_A_alice',             "2-way seed split 'alice' (share A)"),
+		('ss_2way_B_alice',             "2-way seed split 'alice' (share B)"),
+		('ss_2way_join_alice',          "2-way seed join 'alice'"),
+		('ss_2way_join_alice_mix',      "2-way seed join 'alice' (out of order)"),
+		('ss_2way_A_dfl_master3',       '2-way seed split with master share #3 (share A)'),
+		('ss_2way_B_dfl_master3',       '2-way seed split with master share #3 (share B)'),
+		('ss_2way_join_dfl_master3',    '2-way seed join with master share #3'),
+		('ss_2way_A_dfl_usw',           '2-way seed split of user-specified wallet (share A)'),
+		('ss_2way_B_dfl_usw',           '2-way seed split of user-specified wallet (share B)'),
+		('ss_2way_join_dfl_usw',        '2-way seed join of user-specified wallet'),
+		('ss_3way_A_dfl',               '3-way seed split (share A)'),
+		('ss_3way_B_dfl',               '3-way seed split (share B)'),
+		('ss_3way_C_dfl',               '3-way seed split (share C)'),
+		('ss_3way_join_dfl',            '3-way seed join'),
+		('ss_3way_join_dfl_mix',        '3-way seed join (out of order)'),
+		('ss_3way_A_foobar_master7',    "3-way seed split 'φυβαρ' with master share #7 (share A)"),
+		('ss_3way_B_foobar_master7',    "3-way seed split 'φυβαρ' with master share #7 (share B)"),
+		('ss_3way_C_foobar_master7',    "3-way seed split 'φυβαρ' with master share #7 (share C)"),
+		('ss_3way_join_foobar_master7', "3-way seed join 'φυβαρ' with master share #7"),
+		('ss_3way_join_foobar_master7_mix',"3-way seed join 'φυβαρ' with master share #7 (out of order)"),
+
+		('ss_3way_join_dfl_bad_invocation',"bad invocation of 'mmgen-seedjoin' - --id-str with non-master join"),
+		('ss_bad_invocation1',          "bad invocation of 'mmgen-seedsplit' - no arguments"),
+		('ss_bad_invocation2',          "bad invocation of 'mmgen-seedsplit' - master share with split specifier"),
+		('ss_bad_invocation3',          "bad invocation of 'mmgen-seedsplit' - nonexistent file"),
+		('ss_bad_invocation4',          "bad invocation of 'mmgen-seedsplit' - invalid file extension"),
+		('ss_bad_invocation5',          "bad invocation of 'mmgen-seedjoin' - no arguments"),
+		('ss_bad_invocation6',          "bad invocation of 'mmgen-seedjoin' - one file argument"),
+		('ss_bad_invocation7',          "bad invocation of 'mmgen-seedjoin' - invalid file extension"),
+		('ss_bad_invocation8',          "bad invocation of 'mmgen-seedjoin' - nonexistent file"),
+		('ss_bad_invocation9',          "bad invocation of 'mmgen-seedsplit' - bad specifier"),
+		('ss_bad_invocation10',         "bad invocation of 'mmgen-seedsplit' - nonexistent file"),
+		('ss_bad_invocation11',         "bad invocation of 'mmgen-seedsplit' - invalid file extension"),
+	)
+
+	def get_tmp_subdir(self,subdir):
+		return os.path.join(self.tmpdir,subdir)
+
+	def ss_walletgen(self):
+		t = self.spawn('mmgen-walletgen', ['-r0','-p1'])
+		t.passphrase_new('new MMGen wallet',wpasswd)
+		t.label()
+		self.write_to_tmpfile('dfl.sid',t.expect_getend('Seed ID: '))
+		t.expect('move it to the data directory? (Y/n): ','y')
+		t.written_to_file('MMGen wallet')
+		return t
+
+	def ss_splt(self,tdir,ofmt,spec,add_args=[],wf=None,master=None):
+		try: os.mkdir(self.get_tmp_subdir(tdir))
+		except: pass
+		t = self.spawn('mmgen-seedsplit',
+				['-q','-d',self.get_tmp_subdir(tdir),'-r0','-o',ofmt]
+				+ (['-L',(spec or 'label')] if ofmt == 'w' else [])
+				+ add_args
+				+ (['--master-share={}'.format(master)] if master else [])
+				+ ([wf] if wf else [])
+				+ ([spec] if spec else []))
+		if not wf:
+			t.passphrase('MMGen wallet',wpasswd)
+		if spec:
+			from mmgen.obj import SeedSplitSpecifier
+			sss = SeedSplitSpecifier(spec)
+			pat = "Processing .* {} of {} of .* id '{}'".format(sss.idx,sss.count,sss.id)
+		else:
+			pat = "master share #{}".format(master)
+		t.expect(pat,regex=True)
+		if ofmt in ('w','incog','incog_hex','hincog'):
+			desc = {'w':         'MMGen wallet',
+					'incog':     'incognito data',
+					'incog_hex': 'hex incognito data',
+					'hincog':    'hidden incognito data' }[ofmt]
+			t.hash_preset('new '+desc,'1')
+			t.passphrase_new('new '+desc,sh1_passwd)
+			if desc == 'hidden incognito data':
+				t.hincog_create(1234)
+			t.written_to_file(capfirst(desc))
+		else:
+			t.written_to_file('data')
+		return t
+
+	def ss_join(self,tdir,ofmt,in_exts,add_args=[],sid=None,bad_invocation=False,master=None,id_str=None):
+		td = self.get_tmp_subdir(tdir)
+		shares = [get_file_with_ext(td,f) for f in in_exts]
+		if not sid:
+			sid = self.read_from_tmpfile('dfl.sid')
+		t = self.spawn('mmgen-seedjoin',
+				add_args
+				+ (['--master-share={}'.format(master)] if master else [])
+				+ (['--id-str={}'.format(id_str)] if id_str else [])
+				+ ['-d',td,'-o',ofmt]
+				+ (['--label','Joined Wallet Label','-r0'] if ofmt == 'w' else [])
+				+ shares)
+		if bad_invocation:
+			t.read()
+			return t
+		w_enc   = ( 'MMGen wallet' if 'mmdat' in in_exts else
+					'incognito data' if 'mmincog' in in_exts else
+					'hex incognito data' if 'mmincox' in in_exts else
+					'hidden incognito data' if '-H' in add_args else '')
+		if 'incognito' in w_enc:
+			t.hash_preset(w_enc,'1')
+		if w_enc:
+			t.passphrase(w_enc,sh1_passwd)
+		if master:
+			fs = "master share #{}, split id '{}', share count {}"
+			pat = fs.format(master,id_str or 'default',len(shares)+('hidden' in w_enc))
+			t.expect(pat,regex=True)
+		sid_cmp = t.expect_getend('Joined Seed ID: ')
+		cmp_or_die(sid,sid_cmp)
+		if ofmt == 'w':
+			t.hash_preset('new MMGen wallet','1')
+			t.passphrase_new('new MMGen wallet',wpasswd)
+			t.written_to_file('MMGen wallet')
+		else:
+			t.written_to_file('data')
+		return t
+
+	def get_hincog_arg(self,tdir,suf='-default-2of2'):
+		sid = self.read_from_tmpfile('dfl.sid')
+		return os.path.join(self.tmpdir,tdir,sid+suf+'.hincog') + ',123'
+
+	def ss_2way_A_dfl1(self):    return self.ss_splt('2way_dfl1','w','1:2')
+	def ss_2way_B_dfl1(self):    return self.ss_splt('2way_dfl1','bip39','2:2')
+	def ss_2way_join_dfl1(self): return self.ss_join('2way_dfl1','w',['mmdat','bip39'])
+
+	def ss_2way_A_dfl2(self):    return self.ss_splt('2way_dfl2','seed','default:1:2')
+	def ss_2way_B_dfl2(self):
+		return self.ss_splt('2way_dfl2','hincog','default:2:2',['-J',self.get_hincog_arg('2way_dfl2')])
+	def ss_2way_join_dfl2(self):
+		return self.ss_join('2way_dfl2','hex',['mmseed'],['-H',self.get_hincog_arg('2way_dfl2')])
+
+	def ss_2way_A_alice(self):        return self.ss_splt('2way_alice','w','alice:1:2')
+	def ss_2way_B_alice(self):        return self.ss_splt('2way_alice','hex','alice:2:2')
+	def ss_2way_join_alice(self):     return self.ss_join('2way_alice','seed',['mmdat','mmhex'])
+	def ss_2way_join_alice_mix(self): return self.ss_join('2way_alice','seed',['mmhex','mmdat'])
+
+	def ss_2way_A_dfl_usw(self):    return self.ss_splt('2way_dfl_usw','words','1:2',[],wf=ref_wf)
+	def ss_2way_B_dfl_usw(self):    return self.ss_splt('2way_dfl_usw','incog','2:2',[],wf=ref_wf)
+	def ss_2way_join_dfl_usw(self): return self.ss_join('2way_dfl_usw','hex',['mmwords','mmincog'],sid=ref_sid)
+
+	def ss_3way_A_dfl(self):        return self.ss_splt('3way_dfl','words','1:3')
+	def ss_3way_B_dfl(self):        return self.ss_splt('3way_dfl','incog_hex','2:3')
+	def ss_3way_C_dfl(self):        return self.ss_splt('3way_dfl','bip39','3:3')
+	def ss_3way_join_dfl(self):     return self.ss_join('3way_dfl','hex',['mmwords','mmincox','bip39'])
+	def ss_3way_join_dfl_mix(self): return self.ss_join('3way_dfl','hex',['bip39','mmwords','mmincox'])
+
+	def ss_2way_A_dfl_master3(self):
+		return self.ss_splt('2way_dfl_master3','w','',master=3)
+	def ss_2way_B_dfl_master3(self):
+		return self.ss_splt('2way_dfl_master3','bip39','2:2',master=3)
+	def ss_2way_join_dfl_master3(self):
+		return self.ss_join('2way_dfl_master3','hex',['mmdat','bip39'],master=3)
+
+	tdir2 = '3way_foobar_master7'
+	def ss_3way_C_foobar_master7(self):
+		return self.ss_splt(self.tdir2,'hincog','',
+					['-J',self.get_hincog_arg(self.tdir2,'-master7')],master=7)
+	def ss_3way_B_foobar_master7(self):
+		return self.ss_splt(self.tdir2,'bip39','φυβαρ:2:3',master=7)
+	def ss_3way_A_foobar_master7(self):
+		return self.ss_splt(self.tdir2,'hex','φυβαρ:3:3',master=7)
+	def ss_3way_join_foobar_master7(self):
+		return self.ss_join(self.tdir2,'seed', ['bip39','mmhex'],
+							['-H',self.get_hincog_arg(self.tdir2,'-master7')],master=7,id_str='φυβαρ')
+	def ss_3way_join_foobar_master7_mix(self):
+		return self.ss_join(self.tdir2,'seed', ['mmhex','bip39'],
+							['-H',self.get_hincog_arg(self.tdir2,'-master7')],master=7,id_str='φυβαρ')
+
+	def ss_bad_invocation(self,cmd,args,exit_val):
+		t = self.spawn(cmd,args)
+		t.read()
+		t.req_exit_val = exit_val
+		return t
+
+	def ss_3way_join_dfl_bad_invocation(self):
+		t = self.ss_join('3way_dfl','hex',
+				['mmwords','mmincox','bip39'],
+				id_str='foo',
+				bad_invocation=True)
+		t.req_exit_val = 1
+		return t
+
+	def ss_bad_invocation1(self):
+		return self.ss_bad_invocation('mmgen-seedsplit',[],1)
+	def ss_bad_invocation2(self):
+		return self.ss_bad_invocation('mmgen-seedsplit',['-M1','1:9'],1)
+	def ss_bad_invocation3(self):
+		return self.ss_bad_invocation('mmgen-seedsplit',[self.tmpdir+'/no.mmdat','1:9'],1)
+	def ss_bad_invocation4(self):
+		return self.ss_bad_invocation('mmgen-seedsplit',[self.tmpdir+'/dfl.sid','1:9'],1)
+	def ss_bad_invocation5(self):
+		return self.ss_bad_invocation('mmgen-seedjoin',[],1)
+	def ss_bad_invocation6(self):
+		return self.ss_bad_invocation('mmgen-seedjoin',[self.tmpdir+'/a'],1)
+	def ss_bad_invocation7(self):
+		return self.ss_bad_invocation('mmgen-seedjoin',[self.tmpdir+'/a',self.tmpdir+'/b'],1)
+	def ss_bad_invocation8(self):
+		return self.ss_bad_invocation('mmgen-seedjoin',[self.tmpdir+'/a.mmdat',self.tmpdir+'/b.mmdat'],1)
+	def ss_bad_invocation9(self):
+		return self.ss_bad_invocation('mmgen-seedsplit',['x'],1)
+	def ss_bad_invocation10(self):
+		return self.ss_bad_invocation('mmgen-seedsplit',[self.tmpdir+'/a.mmdat','1:2'],1)
+	def ss_bad_invocation11(self):
+		return self.ss_bad_invocation('mmgen-seedsplit',[self.tmpdir+'/dfl.sid','1:2'],1)
diff --git a/test/tooltest2.py b/test/tooltest2.py
index 4345e4e6..2cbf9fd8 100755
--- a/test/tooltest2.py
+++ b/test/tooltest2.py
@@ -330,6 +330,29 @@ tests = {
 				(md5_hash_strip,'996c047e8543d5dde6f82efc3214a6a1')
 			),
 		],
+		'list_shares': [
+			(   ['3','wallet=test/ref/98831F3A.bip39'],
+				(md5_hash_strip,'84e8bdaebf9c816a8a3bd2ebec5a2e12')
+			),
+			(   ['3','id_str=default','wallet=test/ref/98831F3A.mmwords'],
+				(md5_hash_strip,'84e8bdaebf9c816a8a3bd2ebec5a2e12')
+			),
+			(   ['3','id_str=foo','wallet=test/ref/98831F3A.bip39'],
+				(md5_hash_strip,'d2ac20823c4ea26f15234b5ca8df5d6f')
+			),
+			(   ['3','id_str=foo','master_share=0','wallet=test/ref/98831F3A.mmwords'],
+				(md5_hash_strip,'d2ac20823c4ea26f15234b5ca8df5d6f')
+			),
+			(   ['3','id_str=foo','master_share=5','wallet=test/ref/98831F3A.mmwords'],
+				(md5_hash_strip,'c4feedce40bb5959011ee4a996710832')
+			),
+			(   ['3','id_str=βαρ','master_share=5','wallet=test/ref/98831F3A.mmwords'],
+				(md5_hash_strip,'f7d254798fe2e34b94b5f4ff312998db')
+			),
+			(   ['4','id_str=βαρ','master_share=5','wallet=test/ref/98831F3A.bip39'],
+				(md5_hash_strip,'d3e479f55792181372a9f32a569c04e5')
+			),
+		],
 	},
 	'Coin': {
 		'addr2pubhash': {