A computer implemented method of transferring a digital asset, the method comprising: generating, by each first user of a plurality of first users, a respective first blockchain transaction, wherein each said first blockchain transaction has an output unlockable by means of a digital signature of the respective first user of the plurality of first users and a digital signature of a second user to redeem a respective digital asset; generating, by each first user of the plurality of first users, a respective second blockchain transaction, corresponding to said respective first blockchain transaction, wherein each said second blockchain transaction has an input corresponding to the output of the corresponding said first blockchain transaction and has an output unlockable by means of said digital signature of the respective first user of the plurality of first users to redeem the corresponding said digital asset; generating, by each first user of the plurality of first users, a respective third blockchain transaction, corresponding to said respective first blockchain transaction, wherein each said third blockchain transaction has an input corresponding to the output of the corresponding said first blockchain transaction and has an output unlockable by means of a digital signature of a third user to redeem the corresponding said digital asset; sending, by each first user of the plurality of first users, their respective second blockchain transaction to the second user; signing, by the second user, said inputs of each said sent second blockchain transaction with said digital signature of said second user; returning, by the second user, at least each signed said second blockchain transaction, signed with at least the digital signature of the second user, to the respective first users; sending, by each first user of the plurality of first users, their respective third blockchain transaction, not signed with the digital signatures of the corresponding said first users or of the said second user, to the second user; selecting, by the second user, a said sent third blockchain transaction for signing by the corresponding first user and the second user; signing, by the second user, said input of said selected third blockchain transaction with said digital signature of said second user; returning, by the second user, the selected third blockchain transaction, signed with the digital signature of the second user and not signed with the digital signature of the corresponding first user, to the corresponding first user; signing, by the corresponding first user, said input of said selected third blockchain transaction with said digital signature of the corresponding first user; broadcasting, by the corresponding first user, the signed third blockchain transaction to the blockchain to enable the corresponding said digital asset to be redeemed by said third user. generating, by each first user of a plurality of first users, a respective first blockchain transaction, wherein each said first blockchain transaction has an output unlockable by means of a digital signature of the respective first user of the plurality of first users and a digital signature of a second user to redeem a respective digital asset; generating, by each first user of the plurality of first users, a respective second blockchain transaction, corresponding to said respective first blockchain transaction, wherein each said second blockchain transaction has an input corresponding to the output of the corresponding said first blockchain transaction and has an output unlockable by means of said digital signature of the respective first user of the plurality of first users to redeem the corresponding said digital asset; generating, by each first user of the plurality of first users, a respective third blockchain transaction, corresponding to said respective first blockchain transaction, wherein each said third blockchain transaction has an input corresponding to the output of the corresponding said first blockchain transaction and has an output unlockable by means of a digital signature of a third user to redeem the corresponding said digital asset; sending, by each first user of the plurality of first users, their respective second blockchain transaction to the second user; signing, by the second user, said inputs of each said sent second blockchain transaction with said digital signature of said second user; returning, by the second user, at least each signed said second blockchain transaction, signed with at least the digital signature of the second user, to the respective first users; sending, by each first user of the plurality of first users, their respective third blockchain transaction, not signed with the digital signatures of the corresponding said first users or of the said second user, to the second user; selecting, by the second user, a said sent third blockchain transaction for signing by the corresponding first user and the second user; signing, by the second user, said input of said selected third blockchain transaction with said digital signature of said second user; returning, by the second user, the selected third blockchain transaction, signed with the digital signature of the second user and not signed with the digital signature of the corresponding first user, to the corresponding first user; signing, by the corresponding first user, said input of said selected third blockchain transaction with said digital signature of the corresponding first user; broadcasting, by the corresponding first user, the signed third blockchain transaction to the blockchain to enable the corresponding said digital asset to be redeemed by said third user.