A signature server comprising: a processing unit that is configured to, in response to reception of a token issue request including transaction information from a user, generate a permission rule for determining a permission range of transaction contents based on the transaction information and transmit a token corresponding to the permission rule to a web application which processes a proxy transaction for the user, and in response to reception of a signature issue request based on a transaction request by the user including the token from the web application, determine whether or not to issue a digital signature corresponding to the signature issue request, based on whether or not the transaction contents included in the transaction request are within the permission range determined by the permission rule corresponding to the token included in the signature issue request, wherein in a case where a transaction is remittance of an amount of money or points with currency values by the user, the processing unit is configured to determine a permission range of a remittance amount in the permission rule at a time of the token issue request from the user, and determine whether or not the remittance amount included in a remittance request is within the permission range in the permission rule at a time of the remittance request by the user, wherein the processing unit is configured to calculate a value obtained by multiplying the remittance amount included in the transaction information at the time of creating the permission rule by a predetermined coefficient, as a maximum value and a minimum value defining the permission range of the remittance amount. a processing unit that is configured to, in response to reception of a token issue request including transaction information from a user, generate a permission rule for determining a permission range of transaction contents based on the transaction information and transmit a token corresponding to the permission rule to a web application which processes a proxy transaction for the user, and in response to reception of a signature issue request based on a transaction request by the user including the token from the web application, determine whether or not to issue a digital signature corresponding to the signature issue request, based on whether or not the transaction contents included in the transaction request are within the permission range determined by the permission rule corresponding to the token included in the signature issue request, wherein in a case where a transaction is remittance of an amount of money or points with currency values by the user, the processing unit is configured to determine a permission range of a remittance amount in the permission rule at a time of the token issue request from the user, and determine whether or not the remittance amount included in a remittance request is within the permission range in the permission rule at a time of the remittance request by the user, wherein the processing unit is configured to calculate a value obtained by multiplying the remittance amount included in the transaction information at the time of creating the permission rule by a predetermined coefficient, as a maximum value and a minimum value defining the permission range of the remittance amount.